Particles and device for displaying image

ABSTRACT

The present invention intends to provide particles for displaying images used in an image display device capable of displaying and eliminating repeatedly accompanied by flight and movement of particles utilizing Coulomb force, being superior in stability, particularly in repetition durability, memory characteristic stability, adaptability for temperature change, having capability of regulating charge amount, and accordingly, favorable images with sufficient contrast should be stably obtained. The present invention provides particles coated with a resin; specifying Span of particle diameter distribution, charge attenuation property, thermal change of the surface hardness, tensile break strength, Izod impact strength (with a notch), abrasion loss (Taber), tensile elastic modulus, flexural elastic modulus, or tear strength. The present invention also proposes about the structure of the particles.

FIELD OF THE INVENTION

The present invention relates to particles for displaying images used inan image display device that enables to repeatedly display or eliminateaccompanied by flight and movement of fine particles utilizing Coulombforce and the image display device with the use of the particles.

BACKGROUND ART

As an image display device substitutable for liquid crystal device(LCD), image display device (a display) with the use of technology suchas an electrophoresis method, an electrochromic method, a thermalmethod, two colors of particle-rotary method is proposed.

As for these image display device, it is conceivable as inexpensivevisual display device of the next generation from a merit having widefield of vision close to normal printed matter, having smallerconsumption power, and having a memory capability in comparison withLCD, spreading out to a display for portable device, and an electronicpaper is expected.

Recently, electrophoresis method is proposed that micro-encapsulatedispersion liquid made up with dispersion particles and colorationsolution and dispose the liquid between faced substrates. However, inthe electrophoresis method, there is a problem of lacking imagingrepetition stability, because particles with high specific gravity oftitanium oxide is scattered within solution of low specific gravity, itis easy to subside, difficult to maintain a stability of dispersionstate, and difficult in long-term conservation to add dye in solution torender a color. Even in the case of micro-encapsulation, cell size isdiminished to a microcapsule level in order to make it hard to appear,however, an essential problem was not overcome at all.

Besides the electrophoresis method using behavior in the solution asabove-mentioned, recently, a device for displaying wherein two kinds oftoner particles which are different in a color of charging polarity areplaced between a pair of substrates, and an electric field is given tofly and fix the particles to the substrates in different directionwithout using solution is proposed. [The Imaging Society of Japan “JapanHardcopy'99” (Jul. 21-23, 1999) Transaction Pages 249-252, etc.]

Movement mechanism of such a dry visual display device employs asdisplay device with material mixed two kinds in color and chargingpolarity are an electrode substrate and apply the voltage to generate anelectric field between electrode substrates for flying the chargedparticle which have different polarity to a different direction.

The above-mentioned dry process image display device using particlesbehavior in a gas comprising particles and a substrate without using anysolution, there are advantage that a problem such as sedimentation andaggregation of the particles in the electrophoresis method is solved andtransfer resistance of particles is small to make response speed isfaster.

However, with such a dry visual display device, there were the problemsas the following:

-   (1) Structure becomes complicated to dispose the electric charge    transportation layer in one part of a substrate, and a layer of    charge production, which make it difficult to escape an electric    charge from an electroconductive particle constantly, resulting in a    lack of stability.-   (2) Driving voltage becomes greatly large which make it impossible    to move particles unless several hundred volts, comparing to an    electrophoresis method of which particle movement was possible at    around several tens of volts.-   (3) Charge amount of particle itself is a most important parameter    in controlling the force generating by an electric field and    adhesive force between the particles and an electrode substrate.

However, it is difficult that precision control of charge amount inparticle in itself because charge characteristic of particles isinfluenced by materials of particle itself.

In addition, when it is considered that fine particles as displayelement, a color toner of the particle is required to be white or blackso that contrast becomes clear. On the contrary, as polymer fineparticles of general-purpose resin render a clear color, when it becamefine particles, it is possible to employ as particles for white bydiffused reflection of light. However, to get a black particle, it isnecessary to add color and dye of carbon in a polymerization process ofthe particle which make it very difficult to achieve.

-   (4) It is necessary to reduce adhesive force between particles or    between particles and substrates to move particles stably and    repeatedly. For this purpose, the method of coating particles with    low adhesive resin is conceivable; however, a crush process is    necessary because particles cohere at the time of drying in normal    wet processing.-   (5) The particles were generally prepared as spherical particles    using such method as suspension polymerization or emulsion    polymerization dispersing droplets of resin particles into an    aqueous disperse medium, and in the case where white particles are    prepared, they contains titanium oxide, zinc oxide, silicon oxide as    a coloring material. These coloring materials are difficult to be    contained uniformly and sufficiently to the aqueous disperse medium    because they have heavy specific gravity and higher affinity to    water than the droplets.

Additionally, even an indefinite particle of a single resin appears aswhite by diffused reflection of light at the surface, however, in theimage display device of flying and moving particles, a sphericalparticle is ideal in the viewpoint of fluidity. However, the indefiniteparticle is hard to fly restricted by a structural disturbance therebyrequiring a great driving voltage.

-   (6) The particles were generally prepared as spherical particles    using such method as suspension polymerization or emulsion    polymerization dispersing droplets of resin particles into an    aqueous disperse medium, however, they must be characterized by    either positive or negative by the polarity of the applied voltage    so as to determine a flying direction, and enough charge amount is    required for achieving highly efficient flight and movement.-   (7) In an occasion of forming an electric field, an ideal flight of    particles is not realized, and contrast of a display screen is    insufficient for displaying favorable images stably.

The object of the present invention is to provide particles fordisplaying images and image display device having the followingcharacteristic under the situation as above-mentioned, overcoming theproblems in dry image display devices.

-   (a) It is superior in stability and particularly in repetition    durability.-   (b) It is superior in stability and particularly in memory    characteristics.-   (c) It is superior in stability, and particularly in adaptive    characteristics to a temperature change.-   (d) Application of charges to the particle is sufficiently achieved    and, when forming an electric field, an ideal flight of particles is    realized resulting in displaying favorable images with enough    contrast stably.-   (e) Aggregation of the particles is prevented enabling to display    images superior in stability.-   (f) White is distinctly displayed with low driving voltage.-   (g) The application of the character of either positive or negative    to the particles and maintaining the charge amount are easy, and    control of the charge amount is possible.-   (h) When forming an electric field, an ideal flight of particles is    realized to display favorable images with enough contrast stably.

As a result of repeated zealous study by the inventors of the presentinvention to achieve the object, they found the following knowledge andbased on the knowledge, they completed the present invention.

-   (i) By preparing the ingredients for the particles coated with    resin, the image display devices should be schemed for elevated    capability and the durability of the image display device should be    improved.-   (ii) By preparing the ingredients for the particles with a small    Span of the particle diameter distribution, an image with a great    contrast ratio should be obtained and durability should be improved.-   (iii) By preparing the ingredients for the particles with slow    charge attenuation, an image display device superior in stability    and, particularly, in memory characteristic should be obtained.-   (iv) By preparing the ingredients for the particles regulating the    ratio between the surface hardness at the temperature of 0° C. and    the surface hardness at the temperature of 100° C., an image display    device superior in stability and, particularly, in response to the    change of the temperature should be obtained.-   (v) By preparing the ingredients for the particles regulating the    tensile break strength, an image display device superior in    stability and, particularly, in response to the change of the    temperature should be obtained.-   (vi) By preparing the ingredients for the particles regulating Izod    impact strength, an image display device superior in stability and,    particularly, in response to the change of the temperature should be    obtained.-   (vii) By preparing the ingredients for the particles regulating the    abrasion loss (Taber), an image display device superior in stability    and, particularly, in response to the change of the temperature    should be obtained.-   (viii) By preparing the ingredients for the particles regulating the    tensile elastic modulus, an image display device having capability    of displaying the images superior in stability and, particularly, in    repetition durability should be obtained.-   (ix) By preparing the ingredients for the particles regulating the    flexural elastic modulus, an image display device having capability    of displaying the images superior in stability and, particularly, in    repetition durability should be obtained.-   (x) By preparing the ingredients for the particles regulating the    tear strength, an image display device having capability of    displaying the images superior in stability and, particularly, in    repetition durability should be obtained.-   (xi) By preparing a group of combined particles comprising mother    particles whereon many child particles of at least one kind adhere,    an image display device having capability of displaying the images    superior in repetition durability at a low driving voltage, cheap,    and achieving the compatibility of improving stability and reducing    the driving voltage should be obtained.-   (xii) By preparing the ingredients for the particles obtained by    surface treating fine particles with a solution of charge control    agent, attachment of charging ability over the particles should be    sufficiently carried out and an ideal flight and movement should be    realized in an occasion of forming an electric field, and    accordingly, favorable images with sufficient contrast should be    stably obtained.-   (xiii) By preparing the ingredients for the particles obtained by    resin coating them by means of spraying a solution of dissolving    resin, an aggregation of the particles should be prevented and    favorable images with extended longevity against repeating display    and with superior stability should be easily obtained.-   (xiv) By preparing the ingredients for the particles at least one    resin layer is formed as an outer layer over a spherical central    component by coating a resin comprising a component whose index of    refraction is different from that of the central component, an image    display device having capability of displaying white clearly,    quickly responsive, and superior in repetition durability at a low    driving voltage should be obtained.-   (xv) By preparing the ingredients for the particles involving    indefinite particles, around which at least one resin layer is    formed by coating a resin comprising a component whose index of    refraction is different from that of the indefinite particles An    image display device having capability of displaying white clearly,    quickly responsive, and superior in repetition durability at a low    driving voltage should be obtained.-   (xvi) By preparing the ingredients for the particles containing a    resin component prepared by polymerizing at least one kind of    monomer selected from acrylic monomer, methacrylic monomer and    styrenic monomer, an image display device easily determining    positive or negative and ensuring surface charge density, capable of    charge control by the selection of the monomer or blending ratio,    quickly responsive, and superior in repetition durability at a low    driving voltage should be obtained.-   (xvii) By preparing the ingredients for the particles contained in a    mixture obtained by blending at least two kinds of said particles    different in both color and charge characteristic, and by settling a    difference between each surface charge density within the range of 2    to 150 μC/m², an ideal flight and movement of particle under the    formation of the electric field should be realized and accordingly,    favorable images with sufficient contrast and without any unevenness    should be stably obtained.

Namely, the present invention provides particles for displaying imagesused in an image display device which displays images by flying andmoving at least one group of particles enclosed between a pair of facingsubstrates of which at least one is transparent and across thesubstrates, an electric field being applied, wherein the ingredients forthe particles satisfy at least one requirement among the following:

-   (1) they are coated with a resin;-   (2) Span of particle diameter distribution defined by the following    equation is less than 5:    Span=(d _(0.9) −d _(0.1))/d _(0.5)    wherein d_(0.1) represents a particle diameter (μm) of the particles    whose ratio of particles equal to or less than it is 10%, d_(0.5)    represents a particle diameter (μm) defining that 50% of the    particles are greater than this, and another 50% of the particles    are smaller than this, d_(0.9) represents a particle diameter of the    particles whose ratio of particles equal to or smaller than it is    90% each in the particle diameter distribution;-   (3) in the case where the surfaces of the particles are charged by    applying a voltage of 8 kV onto a Corona generator deployed at a    distance of 1 mm from the surface of the particles, a surface    potential of the particle 0.3 second after the discharge is greater    than 300 V;-   (4) a ratio between a surface hardness at 0° C. and a surface    hardness at 100° C. is 1.7 or smaller;-   (5) tensile break strength is 20 MPa or greater;-   (6) Izod impact strength (with a notch) is 100 J/m or greater;-   (7) abrasion loss (Taber) is 22 mg or less;-   (8) tensile elastic modulus is 24.5 MPa or greater;-   (9) flexural elastic modulus is 44.1 MPa or greater;-   (10) tear strength is 100 kg/cm or greater;-   (11) they are a group of combined particles comprising mother    particles whereon many child particles of at least one kind adhere;-   (12) they are obtained by surface treating fine particles by the use    of a solution of charge control agent;-   (13) they are coated with a resin by spraying a solution prepared by    dissolving resin;-   (14) at least one resin layer is formed as an outer layer over a    spherical central component by coating a resin comprising a    component whose index of refraction is different from that of the    central component;-   (15) they involve an indefinite particles around which at least one    resin layer is formed by coating a resin comprising a component    whose index of refraction is different from that of the indefinite    particle; or-   (16) they contain a resin component prepared by polymerizing at    least one kind of monomer selected from acrylic monomer, methacrylic    monomer and styrenic monomer.

The present invention also provides an image display device with the useof the particle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration showing a structure of an image display deviceof the present invention;

FIG. 2 is a figure showing an example of the shape of a substrate in theimage display device of the present invention;

FIG. 3 is a figure showing other example of the shape of the substratein the image display device of the present invention;

FIG. 4 is a figure also showing still other example of the shape of thesubstrate in the image display device of the present invention;

FIG. 5 is a figure showing a structure of particles coated with resin;

FIG. 6 is an illustration of CRT 2000 used for the measurement ofsurface potential;

FIG. 7 is an illustration showing a displaying system in the imagedisplay device of the present invention;

FIG. 8 is an illustration showing another displaying system in the imagedisplay device of the present invention;

FIG. 9 is an illustration showing a structure of the image displaydevice of the present invention;

FIG. 10 is a figure showing an -example of the shape of a partition wallin the image display device of the present invention;

FIG. 11 is an illustration of a process for forming a partition wall byscreen-printing method in the image display device of the presentinvention;

FIG. 12 is an illustration of a process for forming a partition wall bysandblast method in the image display device of the present invention;

FIG. 13 is an illustration of a process for forming a partition wall byphotosensitive paste method in the image display device of the presentinvention;

FIG. 14 is an illustration of a process for forming a partition wall byadditive method in the image display device of the present invention;and

FIG. 15 is an illustration showing a measuring method of the minimumdriving voltage in EXAMPLE.

EXPLANATIONS OF NUMERICAL SYMBOLS ARE AS FOLLOWS

-   1,2: substrate-   3: particles-   4: partition wall-   5: spacer-   6: resin-   7: roll shape charge member-   8: shaft-   9: chuck-   10: corotron discharger-   11: surface potential instrument

THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION

An image display device with the use of the particles for displayingimages of the present invention displays images by flying and moving atleast one group of particles enclosed between a pair of facingsubstrates of which at least one is transparent and across thesubstrates, an electric field being applied.

FIG. 1 is an illustration showing a structure of the image displaydevice. In FIG. 1, substrate 1 and substrate 2 are facing with eachother at a predetermined distance and at least one kind of particles areenclosed. (There are two kinds of particles with different colors inFIG. 1.) At least one of substrate 1 or substrate 2 is a transparentsubstrate enabling to recognize the color of the particle from outside,and a material with a great transmittance of visible light and a greatheat-resistance is preferable.

The presence of flexibility as the image display device is selectedappropriately by the use, for example, the flexible materials areselected for the use as an electronic paper and so on, materials withoutflexibility are selected for the use as display units for portabledevices such as cellular phones, PDAs, notebook-sized personalcomputers.

Examples of the forces acting on the particle for the image displaydevice include an attracting force caused by Coulomb force betweenparticles, an intermolecular force, Coulomb force with an electrodeplate, water bridging power, and gravity.

When the force working on particles by an electric field exceeds thesegeneral forces in the relative forces with each other, a flight andmovement of the particle itself occurs, and accordingly, various kindsof characteristics are required for the particle for displaying images.

The ingredients for the particles for displaying images of the presentinvention satisfies the required various kinds of characteristics bysatisfying at least any one of the foregoing requirements (1) to (16).

The requirement (1) describing that the ingredients for the particlesfor displaying images are coated with a resin will be detailed below:

The ingredients for the particles for displaying images needs to bedesigned so as to move uniformly and stably with repetition, in otherwords, so as to receive Coulomb force, which is uniform and with littledurability change.

However, in accordance with the prior art, it is difficult to make thecharge characteristics of the particle important in Coulomb force and soon (particles movement) compatible with the color characteristic of theparticle important in display. In fact, there is not any particleintentionally changing the charge characteristics and still with thesame color. Means for fixing a charge control agent on the surface ofthe particle can be considered, however, because the surface of theparticle is rubbed in a a reciprocating movement motion, it is difficultto give the charge characteristics of little durability change to theparticle.

The foregoing requirement (1) overcomes these problems by making thesurface of the particles coated with the resin obtaining desired chargecharacteristics and thereby regulating the charge characteristics bymeans of selecting the kind of the resins precisely and quantitativelywith the same color. Further, by increasing the thickness of the resinto a considerable value, the particle for displaying images provides thecharge characteristics of little durability change even though it isrubbed and worn in a reciprocating motion, because there will be thesame kind of resin on the surface of the particles.

Moreover, in an occasion of satisfying the foregoing requirement (1), byselecting a resin with quick charge attenuation as the coating resin,the particles can be designed to easily drivable and to have a superiorlong-term storage property. Specifically, when the particles fordisplaying images move, it becomes possible to effectively move theparticles even with a low voltage by making the charge held surely overthe surface of the particles. Besides, in a case where the image is notdisplayed or is stored in a memory, an aggregation of positively chargedparticles and negatively charged particles should be reduced to improvelong-term storage property by promoting the charge to leak from thesurface of the particles.

Accordingly, the foregoing requirement (1) overcomes the ambivalentproblem in conventional dry-type image display device that with the useof particles having highly sensitive charge characteristics, theparticles move swiftly but aggregate in long-term storage, and with theuse of particles having poorly sensitive charge characteristics, theparticles do not aggregate each other but hardly move to reveal an imagedisplay.

Therefore, the ingredients for the particles for displaying imagessatisfying the foregoing requirement (1) of the present invention arecoated with resin 6 as shown in FIG. 5.

The particles to be coated may be any materials exemplified below andhaving a desired color and capable of being coated, however, sphericalparticles with a small specific gravity is preferable.

Typical examples of the inorganic particles include titanium oxide, zincwhite, zinc sulfide, antimony oxide, calcium carbonate, white lead,talc, silica, calcium silicate, alumina white, cadmium yellow, cadmiumred, cadmium orange, titanium yellow, Berlin blue, sea blue, cobaltblue, cobalt green, cobalt violet, iron oxide, carbon black, manganeseferrite black, cobalt ferrite black, copper powders, and aluminumpowders.

Typical examples of the organic polymer particle include urethane-based,nylon-based, fluorine-based, silicone-based, melamine-based,phenol-based, styrene-based, styrene acryl-based, and urethaneacryl-based polymer particle.

They further include styrene acryl-based hollow particles (availablefrom JSR Co., Ltd., etc.), or thermal expansion type hollow particles(available from Matsumoto Oils and Fats Co., Ltd., etc.).

These particles may be materials colored with pigments or dye. As aresin for coating the particles, although any materials capable ofapplying charge characteristics and of being coated to the particles aresuitable, a selection of a resin with quick charge attenuation ispreferable as described above.

Examples of the resin used for coating include urethane resin, acrylicresin, polyester resin, modified urethane acrylic resin, silicone resin,nylon resin, epoxy resin, styrene resin, butyral resin, vinylidenechloride resin, melamine resin, phenol resin, and fluorocarbon polymers;and two kinds or more of these may be mixed and used. Particularlypreferable examples of positive charge applying resin include nylonresin, epoxy resin, and styrene acrylic resin; and particularlypreferable examples of negative charge applying resin includefluorocarbon polymers, silicone resin, and acryl urethane fluorocarbonpolymers.

As the resin with quick charge attenuation, it is preferable to selectresin corresponding with the surface potential under the followingmeasurement condition:

Namely, applying the voltage of 8 KV to a Corona generator disposed witha distance of 1 mm to the surface to generate Corona discharge, chargingthe surface, and then, measuring the change of the surface potential,determine the suitability. In this occasion, it is preferable to selectthe resin whose surface potential will be 300 V or lower after 0.3seconds, more preferable to select the resin whose surface potentialwill be 200 V or less after 0.3 second as the resin used for coating.

Additionally, the foregoing surface potential is measured by means ofCRT2000 produced by QEA Inc. (Quality Engineering Associates Inc.) inUSA as shown in FIG. 6. In this instrument, both end portions of shaft 8of roll shaped charge member 7 disposing a coating resin over thesurface are held with chuck 9, compact corotron discharger 10 andsurface potential meter 11 are spaced with predetermined interval toform a measurement unit. Facedly deploying the measurement unit with adistance of 1 mm from the surface of the particles to be coated, and bymoving the measurement unit from one end portion of the charge member 7to the other end portion with an uniform speed, with the state that thecharge member 7 remains stopping and while giving surface charge, amethod of measuring its surface potential is preferably adopted.Moreover, measurement environment should be settled at the temperatureof 25±3° C. and the humidity of 55±5% RH.

Examples of means for coating the resin over the particles includedisper coat, coatmizer, and Henschel mixer.

The disper coat consists of a powder feeding part at the upper portionand a multistage distributor that can supply liquid in multistage fromthe crosswise direction, which controls the operating condition of thismultistage distributor for attaching the liquid component to thesurfaces of the particles, and is able to carry out the operation ofmaking the surfaces of the particles wet with the liquid in an extremelyshort time.

The coatmizer provides a resin coating method over the surfaces ofelectro conductive particles by supplying the particles to be coatedinto a jet flow to form a dispersed layer, and colliding mist flow at aposition parallel to the dispersed layer and made with fine particles ofa droplet containing the particles to be coated into the coatedparticles.

As for the amount of resinous coating, 0.01 to 30% by weight to theparticles is preferable, and 0.01 to 10% by weight is more preferable.

Further, an electric charge control agent, a coloring agent, aninorganic additive (lubricant) may be optionally added to the resin forcoating in order to assist the charge characteristics or a colorcharacteristic.

Examples of the electric charge control agent include, but notparticularly specified to, negative charge control agent such assalicylic acid metal complex, metal-containing azo dye, oil-soluble dyeof metal-containing (containing a metal ion or a metal atom), the fourthgrade ammonium salt-based compound, calixarene compound,boron-containing compound (benzyl acid boron complex), andnitroimidazole derivative.

Examples of the positive charge control agent include nigrosine dye,triphenylmethane compound, the fourth grade ammonium salt compound,polyamine resin, and imidazole derivatives.

Additionally, metal oxides such as ultra-fine particles of silica,ultra-fine particles of titanium oxide, ultra-fine particles of alumina,and so on; nitrogen-containing circular compound such as pyridine, andso on, and these derivatives or salts; and resins containing variousorganic pigments, fluorine, chlorine, nitrogen, etc. can be employed asthe electric charge control agent.

As for a coloring agent, various kinds of organic or inorganic pigmentsor dye as will be described below are employable:

Examples of black pigments include carbon black, copper oxide, manganesedioxide, aniline black, and activated carbon.

Examples of yellow pigments include chrome yellow, zinc chromate,cadmium yellow, yellow iron oxide, mineral first yellow, nickel titaniumyellow, navel orange yellow, naphthol yellow S, hanzayellow G,hanzayellow 10G, benzidine yellow G, benzidine yellow GR, quinolineyellow lake, permanent yellow NCG, and tartrazinelake.

Examples of orange pigments include red chrome yellow, molybdenumorange, permanent orange GTR, pyrazolone orange, Balkan orange, Indusrenbrilliant orange RK, benzidine orange G, and Indusren brilliant orangeGK.

Examples of red pigments include red oxide, cadmium red, diachylon,mercury sulfide, cadmium, permanent red 4R, lithol red, pyrazolone red,watching red, calcium salt, lake red D, brilliant carmine 6B, eosinlake, rhodamine lake B, alizarin lake, and brilliant carmine 3B.

Examples of purple pigments include manganese purple, first violet B,and methyl violet lake.

Examples of blue pigments include Berlin blue, cobalt blue, alkali bluelake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanineblue, partially chlorinated phthalocyanine blue, first sky blue, andIndusren blue BC.

Examples of green pigments include chrome green, chromium oxide, pigmentgreen B. Malachite green lake, and final yellow green G.

Examples of extenders include baryta powder, barium carbonate, clay,silica, white carbon, talc, and alumina white.

Furthermore, there are Nigrosine, Methylene Blue, rose bengal, quinolineyellow, and ultramarine blue as various dyes such as basic dye, acidicdye, dispersion dye, direct dye, etc.

These coloring agents may be used alone or in combination of two or morekinds thereof.

Examples of inorganic additives include titanium oxide, zinc white, zincsulfide, antimony oxide, calcium carbonate, white lead, talc, silica,calcium silicate, alumina white, cadmium yellow, cadmium red, cadmiumorange, titanium yellow, Berlin blue, sea blue, cobalt blue, cobaltgreen, cobalt violet, iron oxide, carbon black, manganese ferrite black,cobalt ferrite black, copper powders, and aluminum powders.

Next, the foregoing requirement (2) describing that the ingredients forthe particles for displaying images have Span of specific particlediameter distribution will be detailed below:

In conventional image display device, even if the same voltage (anelectric field) is applied repeatedly, repeatability of particlesmovement falls larger than expectation, so that the durability of imagedisplay is not obtained.

In requirement (2), because positively charged particles and negativelycharged particles move toward opposed direction each other induced by aninfluence other than Coulomb force, considering that the physicalinfluence in this occasion is important, the particle diameterdistribution and the shape of each particle were quantitatively combinedas optimum.

Namely, the requirement (2) requires Span of particle diameterdistribution defined by the following equation is less than 5,preferably less than 3:Span=(d _(0.9) −d _(0.1))/d _(0.5)wherein d_(0.1) represents a particle diameter (μm) of the particleswhose ratio of particles equal to or less than it is 10%, d_(0.5)represents a particle diameter (μm) defining that 50% of the particlesare greater than this, and another 50% of the particles are smaller thanthis, d_(0.9) represents a particle diameter of the particles whoseratio of particles equal to or smaller than it is 90% each in theparticle diameter distribution.

By regulating Span within less than 5, sizes of each particles becomeuniform, and then uniform movement of the particles becomes possible.

Next, the foregoing requirement (3) describing that the ingredients forthe particles for displaying images have a specified surface potentialwill be detailed below:

In conventional image display device, there is a problem that whenparticles with highly sensitive charge characteristics is used in orderto make driving voltage low, particles movement occurs immediately, andalthough making driving voltage low is realized, the particles startaggregating after the repeated use because of its highly sensitivecharge characteristics. Further, there is another problem that whenparticles with poorly sensitive charge characteristics is used in orderto improve long term stability, although the aggregation between theparticles is hard to occur and stability improves, chargecharacteristics of the particle will degrade. As a result, uniformparticle movement will hardly happen and even when the particle reachesto the surface of the substrate, clear images cannot be displayedbecause the adhesion between the particles, and the surface of thesubstrate, so-called memory characteristics, is not sufficient.

In a common sense, a concept of using particles made up of a resin withhigh electric resistance for securing to get a clear image, particularlymemory characteristics, is a matter of course. However, even by usingthe resin with high electric resistance, so-called insulationcharacteristics, it is not sure to achieve the memory characteristic asexpected.

The requirement (3) is based on the knowledge that by specifying thesurface potential of the particles, above-mentioned clear image,particularly improved memory characteristics, will be achieved.

Concretely, rather than the conventional idea of the electricresistance, a new finding about a leak of the electric charge and anattenuation characteristic is important, and as a result of designingparticles showing an optimum charge attenuation characteristic inaccordance with the appropriate evaluation method, the memorycharacteristic is improved by maintaining adhesive force of the particlewith the surface of the substrate for a long time effectively.

Namely, the requirement (3) requires that in the case where the surfaceof the particles are charged by applying a voltage of 8 kV onto a Coronagenerator deployed at a distance of 1 mm from the surface of theparticles A surface potential of the particle 0.3 second after thedischarge is greater than 300 V.

In order to get particles of the foregoing surface potential, it isimportant that a resin composing the surfaces of the particles containsat least one resin with slow charge attenuation. In this occasion, theresin composing the surface of the particle includes the coating resinwhen the particle is coated with the resin satisfying the foregoingrequirement (1). Accordingly, in satisfying the requirement (1), whenthe resin containing at least a resin with slow charge attenuation isused as the coating resin, it satisfies the requirement (3). Therefore,about the case where the entire particles are formed with a resincontaining the resin with slow charge attenuation will be describedbelow:

In the formation of the entire particles with a resin containing theresin with slow charge attenuation, the examples of the resin include,as the description with regard to the forgoing requirement (1) (they arecoated with a resin), urethane resin, acrylic resin, polyester resin,urethane modified acrylic resin, silicone resin, nylon resin, epoxyresin, styrene resin, butyral resin, vinylidene chloride resin, melamineresin, phenol resin, and fluorocarbon polymers; and two or more kinds ofthese may be used in combination. For the purpose of controlling theadhesive force with the substrate, acryl urethane resin, acryl urethanesilicone resin, acryl urethane fluorocarbon polymers, urethane resin,and fluorocarbon polymers are particularly preferable. Electric chargecontrol agent, coloring agent, or inorganic additive may be optionallyadded in order to assist charge characteristics or color characteristicsof the resin composing the particle. The same materials exemplified inthe description regarding the requirement (1) (they are coated with aresin) are employable as these electric charge control agent, coloringagent, and inorganic additive.

Next, regulating a dynamic characteristic of the ingredients for theparticles for displaying images, in other words, regulating the thermalchange of the surface hardness, the tensile break strength, the Izodimpact strength, the abrasion loss (Taber), the tensile elastic modulus,the flexural elastic modulus, and the tear strength [requirements (4) to(10)] will be described below:

In the image display device, it is necessary that the particles moveuniformly and that the stability in a repeated image display or instorage is maintained not withstanding of the temperature change, inother words, it is necessary that the particles move uniformly and thatthe image stability is maintained both within the range of thetemperature change.

However, in the conventional image display device, because a drivingforce for the particles was assumed to be important, the actualsituation was that an electrical characteristic of the particles, whatis called charge characteristic, was emphasized or that thecharacteristic which cannot be covered with an electrical characteristicof the particles is compensated by a driving method by means of adriving voltage.

For example, there is a problem that the use of particles with highlysensitive charge characteristic in order to make the driving voltage lowcauses particle movement immediately, and although making drivingvoltage low is realized, the particles begin to aggregate in a repeateduse because of its highly sensitive charge characteristic. On the otherhand, there is another problem that the use of particles with poorlysensitive charge characteristic in order to improve the repetitiondurability prevents the aggregation between particles and improvesstability, however, the charge characteristic of the particles willdegrade and uniform particle movement will hard to happen; and further,even though the particle reaches to the surface of the substrate, aclear image is hardly displayed because adhesion of the particle withthe surface of the substrate, so-called memory characteristic is notsufficient.

A hint about an improvement of the stability is found that the dynamiccharacteristic of the particles is also important other than the chargecharacteristic of the particles and the driving method. The dynamiccharacteristic of the particles was not much a problem in movingparticles in liquid as electrophoresis method; however, in the case ofthe particle movement in the dry image display device without liquid, itwill be a particularly important factor.

The present invention includes regulating any one of the dynamiccharacteristic of the particle for displaying images, that is, a thermalchange of surface hardness, a tensile break strength, Izod impactstrength, an abrasion loss (Taber), a tensile elastic modulus, aflexural elastic modulus and a tear strength.

The foregoing requirement (4) requires that the thermal change of thesurface hardness is restricted not to cause troubles in a reciprocatingmovement of the particles, in other words, to cause little change in acollision characteristic of the particles under the temperature changewhen the particles move.

Namely, the requirement (4) requires the ingredients for the particlesfor displaying images of the present invention to satisfy that a ratiobetween a surface hardness at 0° C. and a surface hardness at 100° C. is1.7 or smaller, preferably 1.5 or smaller, and more preferably 1.3 orsmaller.

When the ratio exceeds 1.7, a collision characteristic between particlesin the reciprocating movement of the particles will change with thetemperature change and accordingly, a desired stable image displayscannot be obtained.

Regarding the surface hardness of the resin composing particles, surfacehardness at the temperature of 25° C. in accordance with JIS K7215 ispreferably 40 degrees or greater, more preferably 50 degrees or greater,and still further preferably 60 degrees or greater. When the surfacehardness of the resin is less than 40 degrees, one part of particleswill be worn by the reciprocating movement of the particles, andelectric charge control agent will fall down to cause some troubles onthe movement of the particles themselves. Furthermore, the generatedabrasion dregs will also cause troubles on the movement of the particlesthereby resulting in deteriorating stable image display furiously.Additionally, the surface hardness is measured by means of durometer,and the unit will be D scale.

The foregoing requirement (5) regulates tensile break strength in orderto prevent one part of particles from being worn by the reciprocatingmotion of the particles and to prevent the electric charge control agentfrom falling down to cause some troubles on the movement of the particleitself. Furthermore, the generation of any abrasion dregs will beprevented from causing troubles on the movement of the particles therebyresulting in the prevention of deteriorating stable image displayfuriously.

Namely, the requirement (5) requires tensile break strength of theingredients for the particles to be 20 MPa or greater, preferably to be30 MPa or greater. When the tensile break strength is less than 20 MPa,one part of particles will be worn by the reciprocating motion of theparticles, and electric charge control agent will fall down to causesome troubles on the movement of the particles themselves. Furthermore,the generated abrasion dregs will also cause troubles on the movement ofthe particles thereby resulting in deteriorating stable image displayfuriously. Additionally, the tensile break strength is the valuemeasured in accordance with JIS K7113.

The requirement (6) regulates Izod impact strength in order to preventone part of particles from being worn by the reciprocating motion of theparticles, and to prevent the electric charge control agent from fallingdown to cause some troubles on the movement of the particles themselves.Furthermore, the generation of any abrasion dregs will be prevented fromcausing troubles on the movement of the particles thereby resulting inthe prevention of deteriorating stable image display furiously.

Namely, the requirement (6) requires the Izod impact strength (with anotch) of the ingredients for the particle to be 100 J/m or greater,preferably 130 J/m or greater. When the Izod impact strength (with anotch) is less than 100 J/m, one part of particles will be worn by thereciprocating motion of the particles, and electric charge control agentwill fall down to cause some troubles on the movement of the particlesthemselves. Furthermore, the generated abrasion dregs will also causetroubles on the movement of the particles thereby resulting indeteriorating stable image display furiously. Additionally, the Izodimpact strength is the value measured in accordance with ASTM D526 atthe temperature of 23° C.

The requirement (7) regulates the abrasion loss (Taber) in order toprevent one part of particles from being worn by the reciprocatingmovement of the particles, and to prevent the electric charge controlagent from falling down to cause some troubles on the movement of theparticle itself. Furthermore, the generation of any abrasion dregs willbe prevented from causing troubles on the movement of the particlesthereby resulting in the prevention of deteriorating stable imagedisplay furiously.

Namely, the requirement (7) requires the abrasion loss (Taber) of theingredients for the particles to be 22 mg or less, preferably 20 mg orless, and more preferably 15 mg or less. When the abrasion loss (Taber)exceeds 22 mg, one part of particles will be worn by the reciprocatingmotion of the particles and electric charge control agent will fall downto cause some troubles on the movement of the particles themselves.Furthermore, the generated abrasion dregs will also cause troubles onthe movement of the particles thereby resulting in deteriorating stableimage display furiously. Additionally, the abrasion loss (Taber) is thevalue measured in accordance with JIS K7204 under the condition of load9.8 N for 1000 times.

The requirement (8) regulates the tensile elastic modulus in order toprevent one part of particles from being worn by the reciprocatingmotion of the particles, and to prevent the electric charge controlagent from falling down to cause some troubles on the movement of theparticles themselves. Furthermore, the generation of any abrasion dregswill be prevented from causing troubles on the movement of the particlesthereby resulting in the prevention of deteriorating stable imagedisplay furiously.

Namely, the requirement (8) requires the tensile elastic modulus of theingredients for the particles to be 24.5 MPa (250 kg/cm²) or greater,preferably 29.4 MPa (300 kg/cm²) or greater, and more preferably 39.2MPa (400 kg/cm²) or greater. When the tensile elastic modulus of theparticles is less than 24.5 MPa, one part of particles will be worn bythe reciprocating motion of the particles, and electric charge controlagent will fall down to cause some troubles on the movement of theparticles themselves. Furthermore, the generated abrasion dregs willalso cause troubles on the movement of the particles thereby resultingin deteriorating stable image display furiously.

Additionally, the tensile elastic modulus is measured in accordance withJIS-K7113.

The requirement (9) regulates the flexural elastic modulus in order toprevent one part of particles from being worn by the reciprocatingmotion of the particles, and to prevent the electric charge controlagent from falling down to cause some troubles on the movement of theparticles themselves. Furthermore, the generation of any abrasion dregswill be prevented from causing troubles on the movement of the particlesthereby resulting in the prevention of deteriorating stable imagedisplay furiously.

Namely, the requirement (9) requires the flexural elastic modulus of theingredients for the particles to be 44.1 MPa (450 kg/cm²) or greater,preferably 75.2 MPa (750 kg/cm²) or greater, and more preferably 98.1MPa (1000 kg/cm²) or greater. When the flexural elastic modulus of theparticles is less than 44.1 MPa, one part of particles will be worn bythe reciprocating motion of the particles and electric charge controlagent will fall down to cause some troubles on the movement of theparticles themselves. Furthermore, the generated abrasion dregs willalso cause troubles on the movement of the particles thereby resultingin deteriorating stable image display furiously.

Additionally, the flexural elastic modulus is measured in accordancewith ASTM-D790.

The requirement (10) regulates the tear strength in order to prevent onepart of particles from being worn by the reciprocating motion of theparticles, and to prevent the electric charge control agent from fallingdown to cause some troubles on the movement of the particles themselves.Furthermore, the generation of any abrasion dregs will be prevented fromcausing troubles on the movement of the particles thereby resulting inthe prevention of deteriorating stable image display furiously.

Namely, the requirement (10) requires the tear strength of theingredients for the particles to be 100 kg/cm or greater, preferably 150kg/cm or greater, and more preferably 200 kg/cm or greater. When thetear strength of the particles is less than 100 kg/cm, one part ofparticles will be worn by the reciprocating motion of the particles, andelectric charge control agent will fall down to cause some troubles onthe movement of the particles themselves. Furthermore, the generatedabrasion dregs will also cause troubles on the movement of the particlesthereby resulting in deteriorating stable image display furiously.

Additionally, the tear strength is measured in accordance withASTM-D624, using a sample having the thickness of 2 mm.

Next, the foregoing requirement (11) describing that the ingredients forthe particles for displaying images are a group of combined particleswill be detailed below:

The requirement (11) specifies the ingredients for the particles fordisplaying images are a group of combined particles comprising motherparticles whereon many child particles of at least one kind adhere.

In these combined particles, many child particles are used to cover upthe surface of the mother particles, and one kind or a plural number ofkinds may be employed.

It is important that the ratio (B/A) between the average particlediameter d_(0.5) (A) of the mother particles and the average particlediameter d_(0.5) (B) of the child particles in the combined particles is20 or larger, preferably 100 or larger, and more preferably 300 orlarger. Further, the diameter of the child particle is 1 μm or smaller,preferably 0.1 μm or smaller, more preferably 0.05 μm or smaller.

Additionally, d_(0.5) represents a particle diameter (μm) defining that50% of the particles are greater than this, and another 50% of theparticles are smaller than this. (This definition is effective in allthe description below.)

Furthermore, with regard to the particle diameter distribution of themother particles, Span of particle diameter distribution defined by thefollowing equation is less than 5, preferably less than 3:Particle diameter distribution Span=(d _(0.9) −d _(0.1))/d _(0.5)wherein d_(0.1) represents a particle diameter (μm) of the particleswhose ratio of particles equal to or less than it is 10%, d_(0.9)represents a particle diameter of the particles whose ratio of particlesequal to or smaller than it is 90% each in the particle diameterdistribution.

By arranging the particle diameter distribution Span of the motherparticle within the range of less than 5, the size of each particlesbecome uniform each other and a uniform particle movement becomespossible.

Moreover, the average particle diameter d_(0.5) of the mother particlesis preferable to be 0.1 to 50 μm.

By designing the mother particles and the child particles as theforegoing, it is possible to improve stability at the time of repetitionand at the time of storage, and driving voltage can be greatly reduced.

Although the reason why the improvement achieves is not clear, bydisposing fine particles whose particle diameter is less than 20 timesover the surface of the mother particles whose particle diameterdistribution is uniform, it is supposed that the combined particleswhose particle diameter is approximately uniform in macro concept, andthe surfaces of the mother particles form fine rugged structure by thedisposing the child particles in micro concept. Accordingly, it isconsidered that uniformity of particle diameter in macro conceptcontributes to repetition stability improvement in the particlemovement, namely, at the time of durability and storage, and the finerugged structure of the surfaces of the particles in micro conceptcontributes to adhesive force reduction with the substrate correspondingto the driving voltage reduction.

For this reason, it is important not to merely complex the motherparticles and the child particles but to manage and design them withinthe previously described range. A method of complex the mother particlesand the child particles may be a mechano-chemical method fixing thechild particles by applying mechanical energy to drive them into thesurfaces of the mother particles, a mechano-fusion method diffusing andfixing the child particles by applying thermal energy as well asmechanical energy to the surfaces of the mother particles, or a graftingmethod chemically coupling the child particles with the surface of themother particles.

Besides, the preparation of the mother particles themselves or the childparticles themselves may be kneading and crushing of necessary resin,electric charge control agent, coloring agent, and other additives;polymerizing from a monomer; or coating an existing particle with resin,electric charge control agent, coloring agent, or other additives.

Additionally, regarding with the child particles, they may be preparedfrom the above mentioned materials, however, it is preferable to justemploy existing powders, for example, titanium oxide, zinc oxide, zincsulfide, antimony oxide, calcium carbonate, white lead, talc, silica,calcium silicate, alumina white, a cadmium yellow, cadmium red, cadmiumorange, titanium yellow, Berlin blue, sea blue, cobalt blue, cobaltgreen, cobalt violet, iron oxide, carbon black, manganese ferrite black,cobalt ferrite black, copper powders, and aluminum powders. Among these,titanium oxide, zinc oxide, or carbon black is particularly preferable.

Next, the foregoing requirement (12) describing that the ingredients forthe particles for displaying images is obtained by surface treating fineparticles with the use of solution of electric charge control agent willbe described below:

As described above, there is a method of mixing electric charge controlagent into the resin composing the surfaces of the particles (includingcoating resin) to assist the charge characteristic of the particles,however, the requirement (12) controls the charge characteristic of theingredients for the particles for displaying images by surface treatingthe fine particles with the use of the solution of electric chargecontrol agent.

The surface treatment is carried out by adding the fine particles intothe solution made by dissolving electric charge control agent in asolvent, then separating the fine particles with filtration and dryingthem. By dissolving the electric charge control agent into the solvent,and by surface treating the fine particles with the solution, electriccharge control agent will be fixed on the surfaces of the fineparticles, charge control of the fine particles will become possible.

The fine particles as raw materials are polymerized from monomers inmany cases because they are preferably spherical, however, they may beprepared by being coated with resin. Classification operation isoptionally conducted to make the particle diameters uniform each other.Moreover, even besides it, crushing and classifying the resin may obtainthe fine particles. With regard to the electric charge control agent, itis not specified as far as it is soluble in a solvent and charge controlis possible, marketed material is preferably used. The same materialsexemplified in the description regarding the requirement (1) areemployable as these electric charge control agent.

Moreover, by selecting the electric charge control agent, dyeing toblack or deep purple is possible simultaneously with charge control andthe fine particles for black display are obtainable. Namely, dyeing ofthe fine particles is possible with the solution dissolving nigrosinecompound, resin acid modified azine, resin acid modified azine compound,or metal-containing azo compound.

A solvent may be any in which the electric charge control agent issoluble without swelling and dissolution of the fine particles, andalcohol is preferably used as usual.

As for the processing method, adding around 0.1 to 10% of the electriccharge control agent to the solvent and dissolving them by agitationwith mixers are suitable. Then, removing the unsolved component byfiltering the resultant solution, subsequently adding the fine particlesin the filtration, and agitating the solution with mixers again areusual. The particles for displaying images should be obtained by takingout the processed fine particles from this mixture solution with thefiltration, followed by drying with ovens.

Next, the foregoing requirement (13) describing that the ingredients forthe particles for displaying images is coated with a resin by spraying asolution dissolving the resin will be detailed.

The requirement that they are coated with resin was already explainedabout the requirement (1). However, the requirement (13) means thepreparation of a resin coating particles coated with a resin by sprayinga solution dissolving the resin. In this method, a resin of low adhesionmay be employed, and as for the particles made by this method, anadhesive force between particles or between the particles and thesubstrate can be reduced.

The particles (they are called as nuclear particles) to be coated may benormal particles as far as they have a desired color and are able to becoated, however, spherical particles with light specific gravity areparticularly preferable.

Typical examples of the component of the particles to be coated areusually resins including urethane resin, urea resin, acryl acid resin,polyester resin, acryl urethane resin, acryl urethane silicone resin,acryl urethane fluorocarbon polymers, acryl fluorocarbon polymers,silicone resin, acryl silicone resin, epoxy resin, polystyrene resin,styrene acryl acid resin, polyolefin resin, butyral resin, vinylidenechloride resin, melamine resin, phenolic resin, fluorocarbon polymers,polycarbonate resin, polysulfon resin, polyether resin, and polyamideresin.

As the resin used for coating, material of low adhesion is preferable,and examples include urethane resin, acryl acid resin, polyester resin,urethane modified acryl acid resin, silicone resin, nylon resin, epoxyresin, melamine resin, phenol resin, and fluorocarbon polymers, and twokinds or more of these may be employed in combination.

Nylon resin, epoxy resin, styrene acrylic or acid resin is usedpreferably as a positive chargeable resin in particular, andfluorocarbon polymers, silicone resin, acrylic urethane or fluorocarbonpolymers is preferably used as negative chargeable resin.

As for the coating amount of these resins it is preferable to be 0.01 to30% by weight of the nuclear particles, more preferably 0.05 to 20% byweight, further more preferably 0.1 to 10% by weight. When the coatingamount is less than 0.01% by weight, an effect of coating is notexpected, when it exceeds 30% by weight, it becomes hard to revealcharge characteristic.

Further, electric charge control agent, coloring agent, or lubricant maybe added optionally into the coating resin in order to assist chargecharacteristic or a color characteristic of the resin for coating theparticle. The same materials exemplified in the description regardingthe requirement (1) (they are coated with a resin) are employable asthese electric charge control agent, coloring agent, and inorganicadditive.

The particles with low adhesive force and free from aggregation will beobtained by spraying the solution prepared by dissolving the coatingresin into water or organic solvent over the nuclear particles.

Concretely, at the beginning, coating resin is dissolved into water ororganic solvent. In this occasion, it is a matter of course to use thematerial into which the coating resin is dissolvable as the solventdissolving resin, however, materials whose boiling point is high areunfavorable because of its dry process in production, and methanol,ethanol, acetone, or 2-butanone may be used preferably.

In this manner, the prepared coating resin solution is sprayed over thenuclear particles. The spraying may be preferably carried out with thespraying nozzle having an appropriate diameter over nuclear particlesincluded in a treatment container under the reduced pressure, however,it is not limited to this method.

The temperature inside the treatment container needs to be settled tothe temperature sufficiently higher than the boiling point of the wateror the organic solvent so that they will dry immediately. When thesettled temperature is too low, the particle diameter will be too large,because the particles adhere and aggregate in the state that is not dryenough.

Besides, in order to prevent the particles from adhering andaggregating, the spraying is preferably carried out by the method ofspraying the coating resin while agitating the particles intensely. As amethod for agitating the particles, means to rotate an agitation bladeinserted into the lower part of the treatment container is suggested.However, wire netting of #40 mesh may be employed as the bottom face ofthe treatment container and means to introduce compressed air ofelevated temperature may be favorably conducted in parallel because theagitation of the particles becomes more intensive and the drying speedcan be increased. Examples of such unit include Spira-Flow [produced byFreund Industries Co., Ltd] and Agglomaster [produced by Hosokawa MicronCo., Ltd.].

The average particle diameter of the resin coating particles ispreferably 50 μm or smaller, and more preferably 1 to 30 μm. When theparticle diameter is less than this range, charge density of theparticles will be so large that an imaging force to an electrode and asubstrate becomes too strong; resulting in poor following ability at theinversion of its electric field, although the memory characteristic isfavorable. On the contrary, when the particle diameter exceeds thisrange, the following ability becomes rich and the memory characteristicdegrades.

Moreover, defining the average particle diameter d_(0.5) before coatingresin as r_(a) and defining the average particle diameter d_(0.5) aftercoating resin as r_(b), a changing factor R=r_(b)/r_(a) is preferably 5or smaller, and more preferably 3 or smaller.

The foregoing requirement (14) requires that the ingredients for theparticles for displaying image is prepared by coating at least one resinlayer formed as an outer layer over a spherical central component andthe resin comprises a component whose index of refraction is differentfrom that of the central component.

As thus described, by providing the particle structure of having atleast one resin layer formed as an outer layer over a spherical centralcomponent and the resin comprises a component whose index of refractionis different from that of the central component, the light is diffusedby a reflection in interface between the central particles, and theouter layer so that it appears as white. This corresponds to obtainimage display particles which display white clearly with a low drivingvoltage, and the aim of realizing white particles only with resin wasachieved.

Resins are usually employed as the spherical central component andtypical examples include urethane resin, urea resin, acrylic resin,polyester resin, acryl urethane resin, acryl urethane silicone resin,acryl urethane fluorocarbon polymers, acrylic fluorocarbon polymers,silicone resin, acryl silicone resin, epoxy resin, polystyrene resin,styrene acrylic resin, polyolefin resin, butyral resin, vinylidenechloride resin, melamine resin, phenol resin, fluorocarbon polymers,polycarbonate resin, polysulfon resin, polyether resin, and amide resin.

The resin layer as the outer layer preferably contains the componentpolymerizing at least one kind of monomer selected from acrylic monomer,methacrylic monomer and styrenic monomer.

Typical examples of the component polymerizing at least one kind ofmonomer selected from acrylic monomer, methacrylic monomer and styrenicmonomer include acrylic acid monomer, butyl acrylate monomer,methacrylic acid monomer, methachloronitrile monomer, methacrylic acidn-butyl monomer, methacrylic acid t-butyl monomer, methacrylic acidglycidyl monomer, methacrylic acid hydroxyethyl monomer, methacrylicacid 2-(dimethylamino) ethyl monomer, methacrylic acid 2-(diethylamino)ethyl monomer, styrene monomer, and methyl styrene monomer. By providinga resin layer polymerizing these monomers, the intended resin layerwhose index of refraction is different from that of the centralcomponent will be obtained.

The foregoing requirement (15) requires that at least one kind of theingredients for the particles for displaying images involves indefiniteparticles, around which at least one resin layer is formed by coating aresin comprising a component whose index of refraction is different fromthat of the indefinite particles.

As thus described, by preparing the particle structure involvingindefinite particles, around which at least one resin layer is formed bycoating a resin comprising a component whose index of refraction isdifferent from that of the indefinite particle, thereby resulting inspherical particles as a whole, the incident light into the particlesirregularly reflects on the interface with the indefinite particles. Asa result, the light appears as white, and this corresponds to obtainimage display particles which displays white clearly with a low drivingvoltage, and the aim of realizing white particles only with resin wasachieved.

The indefinite particles may be usually obtained by crushing resins. Thenumber of the indefinite particles involved in the particles fordisplaying image may be one or more.

The resin employable for the indefinite particles and for the outerlayer is the same as the resin employable for the central component ofthe spherical particles and for the outer layer described in theprevious explanation about the requirement (14).

The foregoing requirement (16) requires that the ingredients for theparticles for displaying images contains a resin component prepared bypolymerizing at least one kind of monomer selected from acrylic monomer,methacrylic monomer and styrenic monomer.

As thus described, by employing the resin component of radicalpolymerization type using acrylic monomer, methacrylic monomer, orstyrenic monomer as the image display particles, characterization ofpositive or negative and ensuring the surface charge density becomeseasy.

For example, in the case where resin particles of negative charge arerequired, polymerization with styrene as an essential component may becarried out. In the case where resin particles of positive charge arerequired, co-polymerization of acrylic monomer or methacrylic monomerwith methacrylic acid 2-(diethylamino) ethyl, and so on may be carriedout. As thus described, regulating the charge is possible by theselection and the blending ratio of the monomer.

When the surface charge density is poor only with the monomer,regulating the charge is possible easily by dissolving electric chargecontrol agent into the monomer.

Typical examples of the acrylic monomer include acrylic acid monomer,methyl acrylate monomer, butyl acrylate monomer, and acrylonitrilemonomer. Typical examples of the methacrylic monomer include methacrylicacid monomer, methyl methacrylate monomer, methacrylic acid n-butylmonomer, methacrylic acid t-butyl monomer, glycidyl methacrylatemonomer, methacrylic acid hydroxyethyl monomer, metachloronitrilemonomer, methacrylic acid 2-(diethylamino) ethyl monomer, andmethacrylic acid 2-(dimethylamino) ethyl monomer. Examples of thestyrenic monomer include styrene monomer and methyl styrene monomer.Moreover, two kinds or more of these monomers may be employable incombination.

By satisfying at least any one of above mentioned requirements (1) to(16), particles for displaying images superior in variouscharacteristics such as display stability may be provided, however, inorder to further improve display stability, it is effective to managethe stability, particularly the moisture content and asolvent-indissoluble ratio of the particle, that is, the resin composingthe particles. The water absorption of the resin composing the particlesis preferable to be 3% by mass or less, more preferable to be 2% by massor less. Additionally, the water absorption is measured in accordancewith ASTM D570 on the condition of the temperature of 23° C. for 24hours.

Regarding the solvent-indissoluble ratio of the resin composing theparticles, it is preferable that the solvent-indissoluble ratioexpressed by the following equation is 50% or greater, particularly 70%or greater.Solvent-indissoluble ratio (%)=(B/A)×100wherein A represents the weight of said particles before it is immersedinto the solvent, and B represents the weight of said particles afterimmersing it in a non-defective solvent for 24 hours at the temperatureof 25° C.

When the solvent-indissoluble ratio is less than 50%, a bleed generateon the surface of the particles after a long-term storage, which mayhave an influence on the adhesive force with the particles causing sometroubles in the movement of the particles with obstruction to the imagedisplay durability.

Additionally, favorable examples of the solvent for measuring thesolvent-indissoluble ratio (non-defective solvent) include methyl ethylketone and so on for fluorocarbon polymers, methanol and so on forpolyamide resin, methyl ethyl ketone, toluene or so for acrylic urethaneresin, acetone, isopropanol or so for melamine resin, and toluene, etc.for silicone resin.

The particle is preferably spherical considering the relation withfluidity.

The average particle diameter d_(0.5) is preferable to be 0.1 to 50 μm,particularly to be 1 to 30 μm. When the particle diameter is smallerthan this range, charge density of the particle will be so large thatimaging force to the electrode or the substrate may become too strong,resulting in poor following ability on an occasion of the electric fieldbeing inverted although the memory characteristic is favorable. On thecontrary, when the particle diameter exceeds the range, the followingability is favorable, however, the memory characteristic will degrade.

As for the color of the particles, it is preferable to be white and/orblack. However, in the case where the ingredients for the particlessatisfy the foregoing requirement (14) or requirement (15), namely, whenthe particles comprises the center component and the outer layer (resinlayer) with a different index of refraction, they will be white.

Although it is a matter of course that the charge amount of theparticles depends upon the measurement condition, it is understood thatthe charge amount of the particles in the image display device almostdepends upon initial charge amount and an attenuation accompanied by acontact with the substrate, a contact with other particles, or with anelapse of the time. It is also understood that a saturation value ofcharge behavior accompanying with the contact of the charged particlesbecomes the control factor. Inventors of the present invention measuredthe charge amount of the particles in accordance with the measuringmethod using a carrier in blow-off method, and it was found that thesuitable charge amount of the particles for the image display devicecould be predicted by specifying the surface charge density calculatedfrom the measured charge amount.

Measuring method will be described later, however, by means of blow-offmethod, bringing the particles into enough contact with the carrierparticles and measuring the saturated charge amount enables to measurethe charge amount per unit weight, and by pursuing both the the particlediameter and the specific gravity of the particles separately, it ispossible to calculate the surface charge density of the particles.

In the image display device, because the particle diameter of theparticles used is small and the influence of gravity is so small as canbe ignored, specific gravity of the particles does not have influence tothe movement of the particles. However, regarding the charge amount ofthe particles, even though the average charge amount per unit weightcoincides about the particles with the same particle diameter eachother, the charge amount to be held is different in 2 times in the casewhere the specific gravity of the particles is different in 2 times.Accordingly, it was found that the charge characteristic of theparticles used for the image display device will be suitably evaluatedby the surface charge density (unit: μC/m²) without any relation withthe specific gravity.

Here, it is not always preferable that the surface charge density isgreat. In the image display device with particle movement, it ispreferable that the charge amount is few in order to move the particlesin a low electric field (voltage) because when the particle diameter ofthe particles is large, there is the tendency that an electric imagingforce corresponds to a factor mainly determining an electric field(voltage) to fly the particles. Further, when the particle diameter ofthe particles is small, it is preferable that the charge amount is muchin order to move the particles in a low electric field (voltage) becausenon-electric force such as intermolecular force or liquid bridging forcecorresponds to the factor mainly determining the electric field(voltage) to fly the particles. In addition, because it depends upon thesurface characteristics (materials, shape) of the particles greatly, itcannot be specified by merely the particle diameter and the chargeamount unconditionally, however, when the surface charge density of theparticles is appropriate, the particles work to move to the directiontowards an electrode of different polarity by an electric field.

The inventors of the present invention found that by regulating theaverage particle diameter d_(0.5) of the particles and the surfacecharge density within a specified range, the particles may becomepreferably usable particles for the image display device.

Namely, it is desirable that the average particle diameter of theparticles d_(0.5) is within the range of 0.1 to 50 μm and the surfacecharge density of the particles measured and calculated by blow-offmethod with the use of a carrier is within the range of 5 to 150 μC/m²as absolute value. When the absolute value of the surface charge densityis less than this range, response speed to the change of an electricfield will be late, and the memory characteristic degrades. When theabsolute value of the surface charge density exceeds this range, imageforce for the electrode or the substrate will be so strong that thememory characteristic will be favorable, but following ability will bepoor in the case where the electric field is inverted.

In the blow-off method, a mixture of the particles and the carriers areplaced into a cylindrical container with nets at both ends, andhigh-pressure gas is blown from the one end to separate the particlesand the carriers, and then only the particles are blew off from the meshof the net. In this occasion, charge amount of reverse polarity remainson the carriers with the same charge amount of the particles carriedaway out of the container. Then, all of electric flux by this electriccharge are collected to Faraday cage, and are charged across a capacitorwith this amount. Accordingly, the charge amount of the particles isdetermined as Q=C·V (C: capacity, V: voltage across both ends of thecapacitor) by measuring potential of both ends of the capacitor. Andthen, the surface charge density is determined from the value of thischarge amount of the particles, the average particle diameter and thespecific gravity of the particles each measured separately.

Because it is necessary for the particles to hold the charged electriccharge, insulating particles with the volume specific resistance of1×10¹⁰ Ω·cm or greater are preferable, and in particular, insulatingparticles with the volume specific resistance of 1×10¹² Ω·cm or greaterare more preferable.

Manufacture of the particles may be conducted, in the same manners asalready explained, by kneading and crushing necessary resins, electriccharge control agent, coloring agent, and other additives, bypolymerizing from monomers, or by coating the existing particles withresins, electric charge control agent, coloring agent, and otheradditives.

In the case where a group of particles containing a mixture obtained byblending at least two kinds of the foregoing particles different in bothcolor and charge characteristic are employed as the particles fordisplaying images, it is preferable that the surface charge density ofeach particle will be optimized mutually and the average particlediameter will be regulated within a specified range in order that eachparticle will ideally follow the inversion of the electric field.

As described above, the charge amount of the particles in the imagedisplay device almost depends upon initial charge amount and attenuationaccompanied by a contact with the substrate, a contact with otherparticles, or with an elapse of the time; and a saturation value ofcharge behavior accompanying with the contact of the charged particlesbecomes the control factor, however, it is found that regulating theaverage particle diameter d_(0.5) of the particles within a specifiedrange enables to provide usable particles for the image display device.

Particularly in the case where the group of particles containing themixture obtained by blending at least two kinds of the foregoingparticles different in both color and charge characteristic are employedas the particles for displaying images, a saturation value of chargebehavior in contact with the different particles of those kinds is animportant control factor. Accordingly it is important to know thedifference of the charge characteristic, in other words, work functionbetween these two particles regarding charge amount. Inventors of thepresent invention found that when the difference of surface chargedensity are sufficient in the particles, two kinds of particles willhold charge amount of the different polarity by contacting each otherand maintain a function of the movement caused by an electric field.

Namely, the flight of the particles will become capable of ideallyfollowing the application & inversion of the electric field by settlingthe average particle diameter d_(0.5) within 0.1 to 50 μm and bysettling that the difference of the surface charge density measured andcalculated by the use of a carrier and in accordance with blow-offmethod is within the range of 5 to 150 μC/m² in an absolute value.

When the difference of the surface charge density of each particle issmaller than 5 μC/m², the area where the surface charge densitydistribution of these two kinds of particles overlap will increase.Under such situation, the two kinds of particles might not be ideallyseparated by an application of voltage, resulting in incapability ofexhibiting sufficient performance as the display device.

Further, the absolute value of the surface charge density of either oneof the two kinds of the particles is preferable to be within the rangeof 5 to 150 μC/m². In this occasion, the particles will ideally flyinduced by an electric field so that other particles will be physicallyremoved from the surface of the electrode, and as a result, it enablesthe display device to function sufficiently.

Similarly, in the case where the group of particles containing themixture obtained by blending at least two kinds of the foregoingparticles different in both color and charge characteristic are employedas the particles for displaying images, it is preferable to equalize thecharge attenuation characteristic of each particle, thereby improvingmemory characteristic and repetition stability of each particle.

The charge attenuation characteristic of the particles is obtained bysettling so that the surfaces of the particles are charged by a Coronagenerator caused by applying a voltage of 8 kV onto Corona generatordeployed at a distance of 1 mm from the surface of each particle is 100V or smaller, preferably 80 V or smaller at 0.3 second after thedischarge.

Similarly, in the case where the group of particles containing themixture obtained by blending at least two kinds of the foregoingparticles different in both color and charge characteristic are employedas the particles for displaying images, it is preferable to make theaverage particle diameter of each particle close so that each particlecan move towards each direction.

In other words, it is preferable that a ratio (A/B) between the maximumaverage particle diameter (A) of d_(0.5) and the minimum averageparticle diameter (B) of d_(0.5) is 50 or smaller regarding the twokinds or more of the particles of different color and chargecharacteristic.

The image display device of the present invention employs enclosing theforegoing particles for displaying images between the faced substratesat least one of which is transparent.

As such a image display device, there is a displaying system wherein twokinds or more of the particles with different color are moved towards avertical direction with the substrate as shown in FIG. 7, and there isanother displaying system wherein the particles with one kind of colorare moved towards a parallel direction with the substrate as shown inFIG. 8. The particles for displaying images of the present invention maybe adopted to both displaying systems, however, it is desirable that theformer system is adopted from the viewpoint of the stability.

FIG. 9 is an illustration to show one example of the structure of theimage display device of the present invention. It is formed withsubstrate 1 and substrate 2 that are facing each other and particles 3,further partition wall 4 is installed if necessary.

Examples of the substrate material include polymer sheets such aspolyethylene terephthalate, polyeter sulfone, polyethylene, orpolycarbonate, and inorganic sheets such as glass, quartz or so.

The thickness of the substrate is preferably 2 to 5000 μm, morepreferably 5 to 1000 μm. When the thickness is too thin, it becomesdifficult to maintain strength and distance uniformity between thesubstrates, and when the thickness is too thick, vividness and contrastas a display capability degrade, and in particular, flexibility in thecase of using for an electron paper deteriorates.

For the purpose of preventing unnecessary particle movement in thedirection parallel to the substrates, a regular rugged structure may beapplied by etching or so over the surface of the substrate. As shown inFIG. 2, examples from cross sectional direction of the substrate includetriangle-shaped, square-shaped, and semicircular, and examples fromsubstrate plane orientation include square-shaped, triangle-shaped,circular, and line shaped.

Although any area size and height of the rugged structure may besuitable, a part corresponding to the convex section (an area of a framepart) seen from the display side is preferable to be small, and bymaking the area of the frame part small, the vividness of image displayelevates. Accordingly, by the convex part formation, durabilityrepeatability and memory maintenance characteristics improve.

The distance between substrate 1 and substrate 2 is suitably adjusted ina manner where the particles can move and maintain the contrast of imagedisplay, however, it is adjusted usually within 10 to 5000 μm,preferably within 10 to 500 μm.

In the image display device, an electric field is formed between thesubstrates by the application of outside voltage input to electrodes.There are two cases of the electrode composition: establishing on thesubstrate and establishing on the other part being kept away from thesubstrate, for example, on both ends of the image display device, on thepartition wall (described below), or on the outside surface of thesubstrate.

The electrode of this case is formed of electroconductive materialswhich are transparent and having pattern formation capability on atransparent substrate. Metals such as aluminum, silver, nickel, copper,and gold, or transparent electroconductive metal oxides such as ITO,electroconductive tin oxide, and electroconductive zinc oxide, orelectroconductive polymer such as polyaniline, polypyrrole, andpolythiophene all formed in the shape of thin film by sputtering method,vacuum vapor deposition method, CVD method, and coating method are used.Further, materials formed by applying mixed solution of theelectroconductive material with a solvent and a synthetic resin binderover the substrate may be used.

The thickness of the electrode may be suitable unless theelectroconductivity is absent or any obstacle exists in opticaltransparency, and it is preferable to be 3 to 1000 nm, more preferableto be 5 to 400 nm. The outside voltage input of this case may be directcurrent or superimposing alternating current.

Typical examples of the electroconductive material include cationicpolyelectrolyte such as benzyltrimethylammonium chloride,tetrabutylammonium perchlorate, and so on, anionic polyelectrolyte suchas polystyrenesulfonate, polyacrylate, and so on, or electroconductivefine powders of zinc oxide, tin oxide, or indium oxide. In addition,transparent electrode materials can be employed as the facingsubstrates, however, non-transparent electrode materials such asaluminum, silver, nickel, copper, and gold can be also employed.

It is preferable that an insulating coat layer is formed over eachelectrode in order not to leak the electric charge of the chargedparticles. It is particularly favorable that the coat layer employsresin of negative chargeability for positively charged particles andthat the coat layer employs resin of positive chargeability fornegatively charged particles, because the electric charge of the chargedparticles are hard to escape.

Outside application of the voltage to the electrode may be directcurrent or superposing alternating current.

Further, in the case where the electrode is not established on thesubstrate but established in the outside of the substrate separatelywith the substrate, an electrostatic latent image is formed over theouter surface of the substrate, and by making the predetermined chargedparticles with color drawn or repelled towards or from the substrate inan electric field that generates corresponding to the electrostaticlatent image, the particles arranged correspondent with theelectrostatic latent image are observed and recognized through thetransparent substrate from outside of the image display device.Additionally, with regard to the formation of the electrostatic latentimage, there are a transferring formation method wherein anelectrostatic latent image formed by usual electronic photography systemwith the use of electronic photosensitive materials is transferred onthe substrate of electrostatic image display device of the presentinvention, and a direct method wherein an electrostatic latent image isdirectly formed on the substrate by an ion-flow.

In the image display device of the present invention, durabilityrepeatability and maintenance of memory characteristic may be improvedby preventing unnecessary particle movement in a direction parallel withthe substrate by means of subdividing the space between the substrateswith the use of partition wall 4 as shown in FIG. 3, or spacer 5 asshown in FIG. 4. At the same time, the strength of the image displaydevice itself will be elevated because the distance between substrateswill become uniform and the substrates will be reinforced.

The volume population of the particle existing in the space between thefaced substrates is preferable to be 10 to 80%, more preferable to be 10to 60%. When the volume population exceeds 80%, it causes some troublesin the particle movement, and when it is less than 10%, contrast tendsto be indistinct.

As described above, it is effective for display stability improvement tomanage moisture content and solvent-indissoluble ratio of the particle,however, humidity management of gas in cavities surrounding theparticles between the substrates also contributes to display stabilityimprovement. Specifically, the humidity of gas in the cavities is 60% RHor less, preferably 50% RH or less, and more preferably 35% RH or lesseach at the temperature of 25° C.

The cavity means so-called gas environment where the particles contactand remained after subtracting an occupation part of particles 3, adevice sealing portion and a partition wall and/or a spacer provided ifnecessary and which will be described below from the part sandwiched bysubstrate 1 and substrate 2 facing each other.

The kind of the gas is not specified so far as it satisfies thepreviously described humidity range, and suitable examples of the gasinclude dry air, nitrogen, argon, and helium.

Sealing the gas within the device in order to maintain the humidity isnecessary. For example, assembling the particles, the substrate and soon that will be described below under a predetermined humidityenvironment, further providing a seal member and a seal methodpreventing humidity invasion from the outside to obtain the imagedisplay device wherein the gas and the particles are sealed.

In the image display device of the present invention, a partition walllocating between the faced substrates is optionally formed, and thedisplay area may be formed of plural of display cells.

It is preferable to form the partition walls around each displayelement. The partition walls may be formed in two parallel directions.By this structure, unnecessary particle movement in the directionparallel with the substrate is prevented. Further, durabilityrepeatability and memory holding characteristic are assisted. At thesame time, the distance between the substrates is made uniform asreinforcing the strength of an image display panel.

The shape of the partition wall may be adaptively designed depending onthe size of the particle related with the display, and although it isnot particularly restricted, the width of the partition wall is 10 to1000 μm, and preferably 30 to 500 μm, the height of the partition wallis 10 to 5000 μm, and preferably 10 to 500 μm.

On forming the partition wall, both ribs method joining both of thefaced substrates after forming the ribs on them, and a single rib methodforming the rib only on the substrate of one side are considered.However, for aiming to prevent a dislocation at the time of the joining,the partition wall formation by a single rib method is preferable. A gapmay exist on the condition that the partition wall can prevent atraverse movement of the particle.

Display cells formed with the partition walls comprising of those ribsare, as shown in FIG. 10, square-shaped, triangle-shaped, line-shaped,or circular viewing from the direction of substrate plane.

The part corresponding to the sectional portion of the partition wall(an area of a frame part of the display cell) seen from the display sideis preferably as small as possible, so that the vividness of imagedisplay increases. The formation method of the partition wall is notparticularly restricted, however, a screen printing method whereinpastes are overlapped by coating repeatedly on a predetermined positionby screen plate; a sandblast method wherein partition materials arepainted with a desired thickness entirely over the substrate and thenafter coating resist pattern on the partition materials which is wantedto be left as a partition, jetting abrasive to cut and remove partitionmaterials aside from the partition part; lift-off method (additivemethod) wherein a resist pattern is formed on the substrate usingphotopolymer, and then after burying paste into a resist recess,removing the resist; photosensitive paste method wherein thephotosensitive resin composition containing the partition materials isapplied over the substrate and then obtaining a desired pattern byexposure & developing; and mold formation method wherein pastecontaining the partition materials is applied over the substrate andthen forming a partition by compression bonding & pressure forming thedies having rugged structure; and so on are adopted. Further, modifyingthe mold formation method, relief embossing method wherein a reliefpattern provided by a photopolymer composition is used as a mold is alsoadopted.

Typical example of a concrete process of the screen printing methodcomprises, as illustrated in FIG. 11, the following steps:

-   (1) Preparing paste as the partition material.-   (2) Preparing printing plate for printing a partition pattern    comprising stainless mesh, polyester mesh, etc.-   (3) Applying and transferring the paste over one surface of the    substrate by means of the printing plate (if necessary, over the    substrate where the previously described electrode pattern is    formed).-   (4) Curing by application of heat.-   (5) Repeating the steps (3) to (4) until the thickness of the cured    paste reaches a predetermined value (equivalent to the designed    height of the partition wall), and forming desired partition shape.

In this occasion, the printing plate may comprise any meshes capable ofprinting predetermined partition pattern, and examples include a platedmesh processed to secure high tension, metal mesh such as high-tensilematerial mesh, chemical fiber mesh such as polyester mesh, Tetoron mesh,or the combination type mesh adhering polyester mesh between a plateframe and print areas.

Regarding the screen printing, a usual screen printing machine can beused, and the paste is transferred by means of the foregoing printingplate over the substrate with the use of squeegee and scraper.

In this case, the attack angle of the squeegee is 10 to 30 degrees, andpreferably 15 to 25 degrees. The squeegee speed is 5 to 500 mm/sec andpreferably 20 to 100 mm/sec. The squeegee printing pressure is 0.1 to 10kg/cm², preferably 0.5 to 3 kg/cm².

Typical example of a concrete process of the sandblast method comprises,as illustrated in FIG. 12, the following steps:

-   (1) Preparing paste as the partition material.-   (2) Applying the paste over one surface of the substrate (if    necessary, over the substrate where the previously described    electrode pattern is formed) and drying to cure the paste.-   (3) Adhering a dry film photo resist thereupon.-   (4) Leaving only a pattern part to be the partition by exposure and    etching.-   (5) Etching the pattern part where the resist was removed by    sandblasting until a predetermined lib shape is obtained.

In addition, taking care about securing rectilinear propagation ofabrasives jetted from a sandblast nozzle of the sandblast apparatus byadjusting the balance between air pressure on the abrasives and ejectionamount of the abrasives is important on the occasion of sandblasting.This makes final shape of the formed partition wall beautiful, and sideedges of the partition wall particularly decreases because extradiffusion of abrasives reduces.

Further, examples of the abrasives used for sandblast include glassbeads, talc, calcium carbonate, and metal powders.

Typical example of a concrete process of the photosensitive paste methodcomprises, as illustrated in FIG. 13, the following steps:

-   (1) Preparing photosensitive paste containing photopolymer.-   (2) Applying the photosensitive paste over one surface of the    substrate (if necessary, over the substrate where the previously    described electrode pattern is formed).-   (3) Exposing only a pattern part to be the partition by means of a    photo-mask, and curing the photosensitive paste. (Optionally    repeating the steps (2) to (3) until the height of the cured paste    reaches a desired value)-   (4) Developing and removing an uncured part.-   (5) Burning the cured part if necessary.

Additionally, the photosensitive paste essentially comprises inorganicpowders, photopolymer, and light-initiator, and further comprisessolvent, resin, and additives.

Typical example of a concrete process of the additive method comprises,as illustrated in FIG. 14, the following steps:

-   (1) Adhering a photoresist film on the substrate.-   (2) Leaving the photoresist film only on the part between the    partitions to be formed by exposure etching.-   (3) Preparing paste as the partition material and curing.-   (4) Removing the photoresist film and forming a predetermined    partition shape.

The paste as the partitions material essentially comprises inorganicpowders and resin and further comprises solvent and additives. Examplesof the inorganic powders include ceramic powders and glass powders, andthese may be used alone or in combination of two or more kinds thereof.

Typical examples of the ceramic powders include oxide ceramics such asZrO₂, Al₂O₃, CuO, MgO, TiO₂, and ZnO₂, and non-oxide ceramics such asSiC, AlN, and Si₃O₄.

Typical examples of the glass powders include the materials obtained bymelting, cooling, and crushing SiO₂, Al₂O₃, B₂O₃, and ZnO asingredients. In addition, glass transition temperature Tg of the glasspowders is preferably 300 to 500° C. because this temperature rangeenables the burning process at low temperature with a merit of causinglittle damage.

In this occasion, it is suitable that the particle diameter distributionSpan of the inorganic powders for the paste as partition materialexpressed by the foregoing equation is 8 or smaller, preferably 5 orsmaller.

By making the Span smaller than 8, size of the inorganic powders in thepasted will be uniform and a precise partition wall formation will bepossible even though the foregoing steps from applying to curing theabove-mentioned paste is repeated to lamination.

Further, the average particle diameter d_(0.5) of the inorganic powdersin the paste is 0.1 to 20 μm, and preferably 0.3 to 10 μm. By regulatingthem within the range, precise partition wall formation will be possibleunder the previous repeated lamination in a similar manner.

Additionally, these particle diameter distribution and particle diameterare determined in accordance with the foregoing description.

Any resin capable of containing previously described inorganic powdersand forming predetermined partition shape may be employed as the resincontained in the paste for partitions, and examples includethermoplastic resin, thermosetting resin, and reactive resin. Inconsideration of the required partition properties, the molecular weightand the glass transition temperature of the resin should be as large aspossible. Typical examples of the resin include acrylic, styrenic,epoxy-based, phenolic, urethane-based, polyester-based, and urea-based,preferably in particular, acrylic, epoxy-based, urethane-based, andpolyester-based.

Any solvent to be added into the paste for partitions compatible withthe inorganic powders and with the resin may be employed, and examplesinclude aromatic solvent such as phthalic acid ester, toluene, xylene,and benzene; alcoholic solvent such as oxyalcohol, hexanol, and octanol;ester-based solvent such as ester acetate. They are usually added intothe paste in an amount of 0.1 to 50 parts by weight to the inorganicpowders.

Dye, polymerization inhibitor, plasticizer, thickener, dispersion agent,antioxidant, hardening agent, hardening accelerator, or sedimentationinhibitor may be added optionally to the paste.

The paste materials comprising of these is dispersedly blended withkneaders, agitators, or three rollers under a desired prescription.Considering workability, it is favorable that the viscosity is 500 to300000 cps.

In the image display device of the present invention, a method forcharging the particles negatively or positively is not specifiedparticularly, however, Corona discharge method, electrode injectionmethod, and friction method is used

EXAMPLES

The present invention will be described in further detail with referenceto Examples and Comparative Examples, which do not limit the scope ofthe present invention.

Further, the evaluation about particles and the image display device inExamples and Comparative Examples obtained in Examples and ComparativeExamples were carried out in accordance with the following criteria.Additionally, “an average particle diameter” means “d_(0.5)” in thefollowing description.

(1) Surface Potential

With the use of 2000CRT instrument produced by in QEA Co., Ltd.,applying the voltage of 8 KV to Corona generator disposed with adistance of 1 mm to the surface to generate the Corona discharge, andcharging the surface, and then, surface potential after 0.3 seconds wasmeasured. In addition, the measurement environment was settled to thetemperature of 25° C., and the humidity of 55% RH.

(2-1) Coating Amount of Resin −1

With the use of TGA instrument, rising the temperature up to 800° C.with a rising rate of 20° C./min, the coating amount of the resin overthe particles coated with the resin was calculated from the weightchange.

(2-2) Coating Amount of Resin −2

With the use of DSC instrument, rising the temperature up to 800° C.with a rising rate of 20° C./min, the coating amount of the resin overthe particles coated with the resin was calculated from the peak arearatio.

(3) Solvent-Indissoluble Ratio

After immersing each particles into methyl ethyl ketone solvent at thetemperature of 25° C. for 24 hours, they were dried at the temperatureof 100° C. for 5 hours, and then, the weight was measured. With the useof TGA instrument, the weight change of before and after immersing wasmeasured and the solvent-indissoluble ratio was calculated by thefollowing equation:Solvent-indissoluble ratio (%)=(B/A)×100wherein A represents the weight of said particles before it is immersedinto the solvent, and B represents the weight of said particles afterimmersing it in a non-defective solvent for 24 hours at the temperatureof 25° C.(4-1) Evaluation of Display Capability −1

A voltage of 250 V was applied on the assembled image display device,and while inverting the polarity; displays of black & yellow wererepeated.

The evaluation of the display capability was conducted by measuringabout the contrast ratio, at the first stage, after repeating 10000times, and after leaving 5 days with the use of a reflection imagedensity instrument (RD918 produced by Macbeth Co., Ltd, the same below).In this occasion, the contrast ratio is a ratio between reflectiondensity at the time of black display/reflection density at the time ofyellow display. In addition, the ratio between the contrast ratio at thefirst stage and the contrast ratio after repeating 1000 times (or 10000times), or the contrast ratio of after leaving 5 days was determined ascontrast retention.

(4-2) Evaluation of Display Capability −2

A voltage of 250 V was applied on the assembled image display device,and while inverting the polarity; displays of black & yellow wererepeated.

The evaluation of the display capability was conducted by measuringabout the contrast ratio, at the first stage, after repeating 1000times, and after leaving 5 days with the use of a reflection imagedensity instrument (RD918 produced by Macbeth Co., Ltd, the same below).In this occasion, the contrast ratio is a ratio between reflectiondensity at the time of black display/reflection density at the time ofyellow display. In addition, the ratio between the contrast ratio at thefirst stage and the contrast ratio after repeating 1000 times, or thecontrast ratio of after leaving 5 days was determined as contrastretention.

(4-3) Evaluation of Display Capability −3

A voltage of 250 V was applied on the assembled image display device,and while inverting the polarity; displays of black & white wererepeated 10 times and then, a reflection density at the time ofdisplaying black was measured.

Subsequently, in order to confirm the retention, reflection density wasmeasured again after leaving 10 days under the condition of stoppingapplication of a voltage. Moreover, a voltage of 250 V was appliedagain, and while inverting the polarity, whether the display of black &white shows any abnormality or not was confirmed.

(4-4) Evaluation of Display Capability −4

A voltage of 250 V was applied on the assembled image display device,and while inverting the polarity; displays of black & white wererepeated.

Evaluation of display capability was conducted by measuring the contrastratio with the use of a reflection image density instrument. In thisoccasion, the contrast ratio is a ratio between reflection density atthe time of black display/reflection density at the time of whitedisplay. Moreover, leaving the image display device at the temperatureof 0° C., 25° C., and 60° C., the contrast ratio at each temperaturewere measured respectively.

(4-5) Evaluation of Display Capability −5

A voltage of 250 V was applied on the assembled image display device,and while inverting the polarity; displays of black & white wererepeated.

Evaluation of display capability was conducted by measuring the contrastratio at the first stage, and after repeating 10000 times, with the useof a reflection image density instrument. In this occasion, the contrastratio is a ratio between reflection density at the time of blackdisplay/reflection density at the time of white display. In addition,the ratio between the contrast ratio at the first stage and the contrastratio after repeating 10000 times was determined as retention.

(4-6) Evaluation of Display Capability −6

Raising the applied voltage on the assembled image display devicegradually, the voltage enabling to start movement of the particle wasmeasured as the minimum driving voltage. As shown in FIG. 15 as aspecific example, the voltage as the threshold in the relation of theapplied voltage and reflection density was determined as the minimumdriving voltage.

Next, a voltage of the minimum driving voltage plus 10V was applied, andwhile inverting polarity, displays of black & white was repeated.

The evaluation of the display capability was conducted by measuringabout the contrast ratio, at the first stage, after repeating 10000times, and after leaving 5 days with the use of a reflection imagedensity instrument. In this occasion, the contrast ratio is a ratiobetween reflection density at the time of black display/reflectiondensity at the time of white display. In addition, the ratio between thecontrast ratio at the first stage and the contrast ratio after repeating10000 times or after leaving 5 days was determined as retention.

(4-7) Evaluation of Display Capability −7

A voltage of 500 V was applied on the assembled image display device,and while inverting the polarity; displays of black & white wererepeated.

The evaluation of the display capability was conducted by measuringabout the contrast ratio, at the first stage, after repeating 10000times, and after leaving 5 days with the use of a reflection imagedensity instrument. In this occasion, the contrast ratio is a ratiobetween reflection density at the time of black display/reflectiondensity at the time of white display. In addition, the ratio between thecontrast ratio at the first stage and the contrast ratio after repeating10000 times or after leaving 5 days was determined as retention.

(4-8) Evaluation of Display Capability −8

A voltage of 500 V was applied on the assembled image display device,and while inverting the polarity; displays of black & white wererepeated.

The evaluation of the display capability was conducted by measuringabout the contrast ratio, at the first stage, after repeating 10000times, and after leaving 5 days with the use of a reflection imagedensity instrument. In this occasion, the contrast ratio is a ratiobetween reflection density at the time of black display/reflectiondensity at the time of white display.

Furthermore, unevenness at the time of full-scale display was evaluatedin accordance with the following standards.

-   A: Entire surface of about 100% renders coloration of black & white.-   B: White slightly mixes in black display or vice versa.-   C: Black & white considerably mix in the display.    (5) Particle Diameter and Span of Particle Diameter Distribution

Each group of particles was cast into Mastersizer 2000 (brand name,produced by Malvern instruments Ltd.) measuring instrument, and by meansof attached software (software to calculate particle diameterdistribution and particle diameter based on volume standarddistribution), the following value was obtained:Span=(d _(0.9) −d _(0.1))/d _(0.5)wherein d_(0.1) represents a particle diameter (μm) of the particleswhose ratio of particles equal to or less than it is 10%, d_(0.5)represents a particle diameter (μm) defining that 50% of the particlesare greater than this, and another 50% of the particles are smaller thanthis, d_(0.9) represents a particle diameter of the particles whoseratio of particles equal to or smaller than it is 90% each in theparticle diameter distribution.(6) Surface Hardness

The surface hardness of the particles was measured with the use of adurometer by the unit of D scale in accordance with JIS K7215.

(7) Water Absorption

The water absorption of the particle was measured under the measuringcondition at the temperature of 23° C. for 24 hours in accordance withASTM D570.

(8) Tensile Break Strength

The tensile break strength of the particles was measured in accordancewith JIS K7113.

(9) Izod Impact Strength

The Izod impact strength of the particles was measured at thetemperature of 23° C. in accordance with ASTM D256.

(10) Abrasion Loss (Taber)

The abrasion loss (Taber) of the particles was measured under thecondition of under the condition of load 9.8 N for 1000 times inaccordance with JIS K7204.

(11) Tensile Elastic Modulus

The tensile elastic modulus of the particles was measured in accordancewith JIS-K7113.

(12) Flexural Elastic Modulus

The flexural elastic modulus of the particles was measured in accordancewith ASTM-D790.

(13) Tear Strength

The tear strength of the resin was measured in accordance with ASTM-D624about the sample with the thickness of 2 mm.

(14) Average Particle Diameter d_(0.5)

The average particle diameter d_(0.5) of the particles was measured inaccordance with the method described regarding the foregoing requirement(5).

(15) Changing Factor of the Particle Diameter

Coating the particles with a resin and measuring the average particlediameter d_(0.5) before coating resin as r_(a) and measuring the averageparticle diameter d_(0.5) after coating resin as r_(b),

a changing factor: R=r_(b)/r_(a) was obtained,

wherein d_(0.5) represents a particle diameter (μm) defining that 50% ofthe particles are greater than this, and another 50% of the particlesare smaller than this.

(16) Surface Charge Density

As a blow-off powder charge amount measuring instrument, TB-200 producedby Toshiba Chemical Co., Ltd. was used. Two kinds of positive andnegative charging resin were employed as the carriers, and chargedensity per unit area (unit: μC/m²) was measured in each case. Namely,F963-2535 available from Powder TEC Co., Ltd. was employed as a positivecharging carrier (the carrier whose opponent is positively charged anditself tends to be negative) and F921-2535 available from Powder TECCo., Ltd. was employed as negative charging carrier (the carrier whoseopponent is negatively charged and itself tends to be positive).

The surface charge density of the particles was obtained from themeasured charge amount, the average particle diameter and specificgravity of the particles measured separately. In addition, the averageparticle diameter was measured by the foregoing method, and the specificgravity was measured with the use of a hydrometer produced by ShimadzuSeisakusho Ltd. (brand name: Multi Volume Density Meter H1305).

Example A1

Particles A were prepared by selecting black polymerization toner forelectrophotography (spherical particles with particle diameter of 8 μm)as particles to be coated, and also selecting acryl urethane resinEAU65B (available from Asia-kogyo Co., Ltd.)/IPDI series crosslinkingagent Excel-Hardner HX (available from Asia-kogyo Co., Ltd.) as theresin for coating the particles beforehand. Additionally, the ratiobetween EAU65B25 and Excel-Hardner HX was adjusted to be 6:4 expressedas solid content weight ratio for the use.

The particles A coated with resin beforehand were prepared by blowingthe solution provided by dissolving the above-mentioned acryl urethaneresin and crosslinking agent in methylethylketone (MEK) solvent in amisty way as the coating method, into Spira-Flow apparatus (produced byFreund Industries Co., Ltd.), and in the state that the particles to becoated were flowing, the resin was applied over the surface of theparticles, followed by warming.

Particles B were prepared by selecting yellow polymerization toner(spherical particles with particle diameter of 7 μm) forelectrophotography as particles to be coated, and also selectingfluorocarbon polymers-based resin Kyner2751 (available from ElphatochemCo., Ltd.) as the resin for coating the particles beforehand.

The particles B coated with resin beforehand were prepared similarly asthe particles A by blowing the solution provided by dissolving theabove-mentioned fluorocarbon polymers-based resin Kyner2751 in MEKsolvent in a misty way as the coating method, into Spira-Flow apparatus(produced by Freund Industries Co., Ltd.), and in the state that theparticles to be coated were flowing, the resin was applied over thesurface of the particles, followed by warming.

The display device was assembled as follows: Namely, between a pair ofglass substrates both carrying indium oxide electrodes with thethickness of about 500 Å respectively and adjusting the distance with aspacer to 400 μm, the particles A and B above were filled andsurrounding edges of the substrates were bonded with epoxy seriesadhesive jointly enclosing the particles, a display device was obtained.The mixing rate of particles A and particles B was determined to thesame weight each other respectively and the filling factor of theseparticles between the glasses substrates was adjusted to 60% by volume.

The evaluation results about the characteristics of the particles andthe display capability are shown in Table A.

Example A2

The display device was assembled similarly as Example A1 except that theresin for coating the particles A was replaced to nylon resin TORESINEF300 (available from Teikoku Chemical Industry Co., Ltd.) in ExampleA2.

The evaluation results about the characteristics of the particles andthe display capability are shown in Table A.

Example A3

The display device was assembled similarly as Example A1 except that 2phr of charge control agent BONTRON P51 (available from Orient ChemicalCo., Ltd.) was added to the resin for coating the particles A in ExampleA3.

The evaluation results about the characteristics of the particles andthe display capability are shown in Table A. Because the charge controlagent was added, the contrast turned better a little.

Example A4

The display device was assembled similarly as Example A1 except that thespraying condition of coating was arranged and the amount of the coatingresin was increased in the preparation of the particles A.

The evaluation results about the characteristics of the particles andthe display capability are shown in Table A. Because the amount of thecoating resin was increased, the durability (retention factor) decreaseda little.

Example A5

The display device was assembled similarly as Example A1 except that theresin for coating the particles A was replaced to the mixture of epoxyresin AER6071 (available from Asahi Chemical Industry Co., Ltd.) andhardening agent Sumicure M (available from Sumitomo Chemical Co., Ltd.)with the mixing ratio of 7:2 in Example A5.

The evaluation results about the characteristics of the particles andthe display capability are shown in Table A.

Example A6

The display device was assembled similarly as Example A1 except that theresin for coating the particles A was only acryl urethane resin EAU65B(available from Asia-kogyo Co., Ltd.) in Example A6.

The evaluation results about the characteristics of the particles andthe display capability are shown in Table A. Because the crosslinkingagent was not used, extravagant degradation in preservation was found.

Comparative Example A1

The display device was assembled similarly as Example A1 except thatboth the particles A and the particles B were used bare without coatingresin in Comparative Example A1.

The evaluation results about the characteristics of the particles andthe display capability are shown in Table A. Both the contrast ratio andthe durability (retention) were poor.

Example B1

Black polymerization toner for electrophotography (spherical particleswith particle diameter of 7 μm) were employed as the particles A.

The display device was assembled as follows: Namely, between a pair ofglass substrates both carrying indium oxide electrodes with thethickness of about 500 Å respectively and adjusting the distance with aspacer to 400 μm, the particles A and B above were filled andsurrounding edges of the substrates were bonded with epoxy seriesadhesive jointly enclosing the particles, a display device was obtained.The mixing rate of the particles A and the particles B was determined tothe same weight each other respectively and the filling factor of theseparticles between the glasses substrates was adjusted to 60% by volume.The evaluation results are shown in Table B.

Example B2

The display device was assembled similarly as Example B1 except that theparticles A were replaced to black ground toner for electrophotography(ground classification type with particle diameter of 9 μm) in ExampleB2. The evaluation results are shown in Table B.

Example B3

The display device was assembled similarly as Example B1 except that theparticles A were replaced to carbon microbeads PC (available from NipponCarbon Co., Ltd.) in Example B3. The evaluation results are shown inTable B.

Example B4

The display device was assembled similarly as Example B1 except that theparticles A were prepared as the following: As for particles A, 4 phr ofcarbon black (CB) and 2 phr of BONTRON N07 (available from OrientChemical Co., Ltd.) as charge control agent were added into epoxy-basedresin AER6071 (available from Asahi Chemical Industry Co., Ltd.; withoutaddition of croosslinking agent), and after kneading with the use ofdual-shaft extruder, the mixture was crushed with Jetmill and classifiedinto particles. The evaluation results are shown in Table B.

Because they were without addition of croosslinking agent, thesolvent-indissoluble ratio of the particles A in the solvent was smalland extravagant degradation in storage was found.

Example B5

The display device was assembled similarly as Example B1 except that theparticles A were replaced to carbon microbeads MSB (available fromNippon Carbon Co., Ltd.) in Example B5. The evaluation results are shownin Table B.

Comparative Example B1

The display device was assembled similarly as Example B1 except that theparticles A were replaced to carbon microbeads ISB (available fromNippon Carbon Co., Ltd.) in Comparative Example B1. The evaluationresults are shown in Table B.

Example C1

As for particles A, 4 phr of carbon black (CB) and 2 phr of BONTRON N07(available from Orient Chemical Co., Ltd.) as charge control agent wereadded into acryl urethane resin EAU206B (available from Asia-kogyo Co.,Ltd.) and isophorone-di-isocianate (IPDI)-based crosslinking agentExcel-Hardner HX (available from Asia-kogyo Co., Ltd.), and afterkneading, the mixture was crushed with Jetmill and classified intoparticles.

As for particles B, 10 phr of titanium oxide and 2 phr of BONTRON E89(available from Orient Chemical Co., Ltd.) as charge control agent wereadded into acryl urethane resin EAU206B (available from Asia-kogyo Co.,Ltd.) and IPDI-based crosslinking agent Excel-Hardner HX (available fromAsia-kogyo Co., Ltd.), and after kneading, the mixture was crushed withJetmill and classified into particles.

Between a pair of glass substrates both carrying indium oxide electrodeswith the thickness of about 500 Å respectively and adjusting thedistance with a spacer to 400 μm, the particles A and B above werefilled and surrounding edges of the substrates were bonded with epoxyseries adhesive jointly enclosing the particles, a display device wasobtained. The mixing rate of the particles A and the particles B wasdetermined to the same weight each other respectively and the fillingfactor of these particles between the glasses substrates was adjusted to60% by volume. The evaluation results are shown in Table C. There was noextraordinary phenomenon in shelf life.

Example C2

The display device was assembled similarly as Example D1 except that theresin composing the particles A and the particles B was replaced toacryl urethane resin EAU205B (available from Asia-kogyo Co., Ltd.) andIPDI-based crosslinking agent Excel-Hardner HX (available fromAsia-kogyo Co., Ltd.) in Example C2. The evaluation results are shown inTable C. There was no extraordinary phenomenon in shelf life.

Example C3

The display device was assembled similarly as Example C1 except that theresin composing the particles A and the particles B was replaced toacryl urethane resin EAU205B (available from Asia-kogyo Co., Ltd.) inExample C3. The evaluation results are shown in Table C. Because thecrosslinking agent was not used, degradation in storage was found.

Comparative Example C1

The display device was assembled similarly as Example C1 except that theresin composing the particles A and the particles B was replaced toacryl urethane resin EAU188B (available from Asia-kogyo Co., Ltd.) andIPDI-based crosslinking agent Excel-Hardner HX (available fromAsia-kogyo Co., Ltd.) in Comparative Example C1. The evaluation resultsare shown in Table C. There was no extraordinary phenomenon in shelflife.

Example D1

As for particles A, 4 parts by mass (phr) of carbon black (CB) and 2parts by mass (phr) of BONTRON N07 (available from Orient Chemical Co.,Ltd.) as charge control agent were added into acrylurethane resinEAU204B (available from Asia-kogyo Co., Ltd.) andisophorone-di-isocianate (IPDI)-based crosslinking agent Excel-HardnerHX (available from Asia Kogyo Co., Ltd.), and after kneading, themixture was crushed with Jetmill and classified into particles.

As for particles B, 10 phr of titanium oxide and 2 phr of BONTRON E89(available from Orient Chemical Co., Ltd.) as charge control agent wereadded into acrylurethane resin EAU204B (available from Asia-kogyo Co.,Ltd.) and IPDI-based crosslinking agent Excel-Hardner HX (available fromAsia-kogyo Co., Ltd.), and after kneading, the mixture was crushed withJetmill and classified into particles.

Between a pair of glass substrates both carrying indium oxide electrodeswith the thickness of about 500 Å respectively and adjusting thedistance with a spacer to 400 μm, the particles A and B above werefilled and surrounding edges of the substrates were bonded with epoxyseries adhesive jointly enclosing the particles, a display device wasobtained. The mixing rate of the particles A and the particles B wasdetermined to the same weight each other respectively and the fillingfactor of these particles between the glass substrates was adjusted to60% by volume. The evaluation results are shown in Table D. There was noextraordinary phenomenon in shelf life.

Example D2

The display device was assembled similarly as Example D1 except that theresin composing the particles A and the particles B was replaced toacryl urethane resin EAU203B (available from Asia-kogyo Co., Ltd.) andIPDI-based crosslinking agent Excel-Hardner HX (available fromAsia-kogyo Co., Ltd.) in Example D2. The evaluation results are shown inTable D. There was no extraordinary phenomenon in shelf life.

Example D3

The display device was assembled similarly as Example D1 except that theresin composing the particles A and the particles B was replaced toacryl urethane resin EAU203B (available from Asia-kogyo Co., Ltd.) andIPDI-based crosslinking agent Excel-Hardner HX (available fromAsia-kogyo Co., Ltd.) in Example D3. The evaluation results are shown inTable D. There was no extraordinary phenomenon in shelf life.

Example D4

The display device was assembled similarly as Example D1 except that theresin composing the particles A and the particles B was replaced toacryl urethane resin EAU203B (available from Asia-kogyo Co., Ltd.) inExample D4. The evaluation results are shown in Table D. Because thecrosslinking agent was not used, degradation in storage was found.

Comparative Example D1

The display device was assembled similarly as Example D1 except that theresin composing the particles A and the particles B was replaced toacryl urethane resin EAU53B (available from Asia-kogyo Co., Ltd.) andIPDI-based crosslinking agent Excel-Hardner HX (available fromAsia-kogyo Co., Ltd.) in Comparative Example D1. The evaluation resultsare shown in Table D. There was no extraordinary phenomenon in shelflife.

Example E1

As for particles A, 4 parts by mass (phr) of carbon black (CB) and 2parts by mass (phr) of BONTRON N07 (available from Orient Chemical Co.,Ltd.) as charge control agent were added into 100 parts by mass ofthermoplastic polyether ester elastomer: Hytrel7247 (available fromDUPONT TORAY CO., LTD.), and after kneading, the mixture was crushedwith Jetmill and classified into particles.

As for particles B, 10 parts by mass (phr) of titanium oxide and 2 partsby mass (phr) of BONTRON E89 (available from Orient Chemical Co., Ltd.)as charge control agent were added into 100 parts by mass ofthermoplastic polyether ester elastomer: Hytrel7247 (available fromDUPONT TORAY CO., LTD.), and after kneading, the mixture was crushedwith Jetmill and classified into particles.

Between a pair of glass substrates both carrying indium oxide electrodeswith the thickness of about 500 Å respectively and adjusting thedistance with a spacer to 400 μm, the particles A and B above werefilled and surrounding edges of the substrates were bonded with epoxyseries adhesive jointly enclosing the particles, a display device wasobtained. The mixing rate of the particles A and the particles B wasdetermined to the same weight each other respectively and the fillingfactor of these particles between the glasses substrates was adjusted to60% by volume. Further, the display device was assembled under themanaged air conditioning of at the temperature of 25° C. and thehumidity of 50% RH. The evaluation results are shown in Table E.

Example E2

The display device was assembled similarly as Example E1 except that theresin composing the particles was replaced to thermoplastic polyetherester elastomer: Hytrel5557 (available from DUPONT TORAY CO., LTD.) inExample E2. The evaluation results are shown in Table E.

Reference Example E1

The display device was assembled similarly as Example E1 except that thefilling factor of the particles between the glass substrates was variedto 90% by volume in Reference Example E1. The evaluation results areshown in Table E.

Comparative Example E1

The display device was assembled similarly as Example E1 except that theresin composing the particles was replaced to thermoplastic polyetherester elastomer: Hytrel4057 (available from DUPONT TORAY CO., LTD.) inComparative Example E1. The evaluation results are shown in Table E.

Comparative Example E2

The display device was assembled similarly as Example E1 except that theresin composing the particles was replaced to nylon resin: TORESIN EF300(available from Teikoku Chemical Industry Co., Ltd.) in ComparativeExample E2. The evaluation results are shown in Table E.

Example F1

As for particles A, 4 parts by mass (phr) of carbon black (CB) and 2parts by mass (phr) of BONTRON N07 (available from Orient Chemical Co.,Ltd.) as charge control agent were added into 100 parts by mass ofthermoplastic polyether ester elastomer: Hytrel2751 (available fromDUPONT TORAY CO., LTD.), and after kneading, the mixture was crushedwith Jetmill and classified into particles.

As for particles B, 10 parts by mass (phr) of titanium oxide and 2 partsby mass (phr) of BONTRON E89 (available from Orient Chemical Co., Ltd.)as charge control agent were added into 100 parts by mass ofthermoplastic polyether ester elastomer: Hytrel2751 (available fromDUPONT TORAY CO., LTD.), and after kneading, the mixture was crushedwith Jetmill and classified into particles.

Between a pair of glass substrates both carrying indium oxide electrodeswith the thickness of about 500 Å respectively and adjusting thedistance with a spacer to 400 μm, the particles A and B above werefilled and surrounding edges of the substrates were bonded with epoxyseries adhesive jointly enclosing the particles, a display device wasobtained. The mixing rate of the particles A and the particles B wasdetermined to the same weight each other respectively and the fillingfactor of these particles between the glasses substrates was adjusted to60% by volume. The evaluation results are shown in Table F.

Example F2

The display device was assembled similarly as Example F1 except that theresin composing the particles was replaced to thermoplastic polyetherester elastomer: Hytrel2571 (available from DUPONT TORAY CO., LTD.) inExample F2. The evaluation results are shown in Table F.

Reference Example F1

The display device was assembled similarly as Example F1 except that thefilling factor of the particles between the glasses substrates wasvaried to 90% by volume in Reference Example F1. The evaluation resultsare shown in Table F.

Comparative Example F1

The display device was assembled similarly as Example F1 except that theresin composing the particles was replaced to thermoplastic polyetherester elastomer: Hytrel4047 (available from DUPONT TORAY CO., LTD.) inComparative Example F1. The evaluation results are shown in Table F.

Comparative Example F2

The display device was assembled similarly as Example F1 except that theresin composing the particles was replaced to thermoplastic polyetherester elastomer: Hytrel3548 (available from DUPONT TORAY CO., LTD.) inComparative Example F2. The evaluation results are shown in Table F.

Example G1

As for particles A, 4 parts by mass (phr) of carbon black (CB) and 2parts by mass (phr) of BONTRON N07 (available from Orient Chemical Co.,Ltd.) as charge control agent were added into 100 parts by mass ofthermoplastic polyether ester elastomer: Hytrel6347 (available fromDUPONT TORAY CO., LTD.), and after kneading, the mixture was crushedwith Jetmill and classified into particles.

As for particles B, 10 parts by mass (phr) of titanium oxide and 2 partsby mass (phr) of BONTRON E89 (available from Orient Chemical Co., Ltd.)as charge control agent were added into 100 parts by mass ofthermoplastic polyether ester elastomer: Hytrel6347 (available fromDUPONT TORAY CO., LTD.), and after kneading, the mixture was crushedwith Jetmill and classified into particles.

Between a pair of glass substrates both carrying indium oxide electrodeswith the thickness of about 500 Å respectively and adjusting thedistance with a spacer to 400 μm, the particles A and B above werefilled and surrounding edges of the substrates were bonded with epoxyseries adhesive jointly enclosing the particles, a display device wasobtained. The mixing rate of the particles A and the particles B wasdetermined to the same weight each other respectively and the fillingfactor of these particles between the glasses substrates was adjusted to60% by volume. The evaluation results are shown in Table G.

Example G2

The display device was assembled similarly as Example G1 except that theresin composing the particles was replaced to thermoplastic polyetherester elastomer: Hytrel6347M (available from DUPONT TORAY CO., LTD.) inExample G2. The evaluation results are shown in Table G.

Reference Example G1

The display device was assembled similarly as Example G1 except that thefilling factor of the particles between the glasses substrates wasvaried to 90% by volume in Reference Example G1. The evaluation resultsare shown in Table G.

Comparative Example G1

The display device was assembled similarly as Example G1 except that theresin composing the particles was replaced to thermoplastic polyetherester elastomer: Hytrel7247M (available from DUPONT TORAY CO., LTD.) inComparative Example G1. The evaluation results are shown in Table G.

Comparative Example G2

The display device was assembled similarly as Example G1 except that theresin composing the particles was replaced to thermoplastic polyetherester elastomer: Hytrel7247 F (available from DUPONT TORAY CO., LTD.) inComparative Example G2. The evaluation results are shown in Table G.

Example H1

As for particles A, 4 parts by mass (phr) of carbon black (CB) and 2parts by mass (phr) of BONTRON N07 (available from Orient Chemical Co.,Ltd.) as charge control agent were added into 100 parts by mass ofthermoplastic polyether ester elastomer: Hytrel7247L-01 (available fromDUPONT TORAY CO., LTD.), and after kneading, the mixture was crushedwith Jetmill and classified into particles.

As for particles B, 10 parts by mass (phr) of titan oxide and 2 parts bymass (phr) of BONTRON E89 (available from Orient Chemical Co., Ltd.) ascharge control agent were added into 100 parts by mass of thermoplasticpolyether ester elastomer: Hytrel7247L-01 (available from DUPONT TORAYCO., LTD.), and after kneading, the mixture was crushed with Jetmill andclassified into particles.

Between a pair of glass substrates both carrying indium oxide electrodeswith the thickness of about 500 Å respectively and adjusting thedistance with a spacer to 400 μm, the particles A and B above werefilled and surrounding edges of the substrates were bonded with epoxyseries adhesive jointly enclosing the particles, a display device wasobtained. The mixing rate of the particles A and the particles B wasdetermined to the same weight each other respectively and the fillingfactor of these particles between the glasses substrates was adjusted to60% by volume. The evaluation results are shown in Table H.

Example H2

The display device was assembled similarly as Example H1 except that theresin composing the particles was replaced to thermoplastic polyetherester elastomer: Hytrel6347L-01 (available from DUPONT TORAY CO., LTD.)in Example H2. The evaluation results are shown in Table H.

Reference Example H1

The display device was assembled similarly as Example H1 except that thefilling factor of the particles between the glass substrates was variedto 90% by volume in Reference Example H1. The evaluation results areshown in Table H.

Comparative Example H1

The display device was assembled similarly as Example H1 except that theresin composing the particles was replaced to thermoplastic polyetherester elastomer: Hytrel6347G10 (available from DUPONT TORAY CO., LTD.)in Comparative Example H1. The evaluation results are shown in Table H.

Comparative Example H2

The display device was assembled similarly as Example H1 except that theresin composing the particles was replaced to nylon resin: TORESIN EF300(available from Teikoku Chemical Industry Co., Ltd.) in ComparativeExample H2. The evaluation results are shown in Table H.

Example J1

As for particles A, 4 phr of carbon black (CB) and 2 phr of BONTRON N07(available from Orient Chemical Co., Ltd.) as charge control agent wereadded into thermoplastic polyether ester elastomer: Hytrel5077(available from DUPONT TORAY CO., LTD.), and after kneading, the mixturewas crushed with Jetmill and classified into particles.

As for particles B, 10 phr of Titanium oxide and 2 phr of BONTRON N07(available from Orient Chemical Co., Ltd.) as charge control agent wereadded into thermoplastic polyether ester elastomer: Hytrel5077(available from DUPONT TORAY CO., LTD.), and after kneading, the mixturewas crushed with Jetmill and classified into particles.

Between a pair of glass substrates both carrying indium oxide electrodeswith the thickness of about 500 Å respectively and adjusting thedistance with a spacer to 400 μm, the particles A and B above werefilled and surrounding edges of the substrates were bonded with epoxyseries adhesive jointly enclosing the particles, a display device wasobtained. The mixing rate of the particles A and the particles B wasdetermined to the same weight each other respectively and the fillingfactor of these particles between the glasses substrates was adjusted to60% by volume. As a gas fulfilling the remained cavities, air withrelative humidity of 50% RH was employed. The evaluation results areshown in Table J.

Example J2

The display device was assembled similarly as Example J1 except that theresin composing the particles was replaced to thermoplastic polyetherester elastomer: Hytrel5077 (available from DUPONT TORAY CO., LTD.) inExample J2. The evaluation results are shown in Table J.

Example J3

The display device was assembled similarly as Example J1 except that thefilling factor of the particles between the glass substrates was variedto 90% by volume Example J3. The evaluation results are shown in TableJ. Because the volume population of the particles was great, thecontrast turned worse a little.

Example J4

The display device was assembled similarly as Example J1 except that therelative humidity of the gas in the spaces surrounding the particles wasvaried to 70% RH at 25° C. in Example J4. The evaluation results areshown in Table J. Because the humidity of the gas in the cavities washigh, durability deteriorated a little.

Comparative Example J1

The display device was assembled similarly as Example J1 except that theresin composing the particles was replaced to thermoplastic polyetherester elastomer: Hytrel3548W (available from DUPONT TORAY CO., LTD.) inComparative Example J1. The evaluation results are shown in Table J.Because the tensile elastic modulus of the resin was small and becausethe water absorption was large, degradation of durability wastremendous.

Example K1

As for particles A, 4 phr of carbon black (CB) and 2 phr of BONTRON N07(available from Orient Chemical Co., Ltd.) as charge control agent wereadded into 100 parts by mass of thermoplastic polyether ester elastomer:Hytrel6377 (available from DUPONT TORAY CO., LTD.), and after kneading,the mixture was crushed with Jetmill and classified into particles.

As for particles B, 10 phr of Titanium oxide and 2 phr of BONTRON N07(available from Orient Chemical Co., Ltd.) as charge control agent wereadded into 100 parts by mass of thermoplastic polyether ester elastomer:Hytrel6377 (available from DUPONT TORAY CO., LTD.), and after kneading,the mixture was crushed with Jetmill and classified into particles.

Between a pair of glass substrates both carrying indium oxide electrodeswith the thickness of about 500 Å respectively and adjusting thedistance with a spacer to 400 μm, the particles A and B above werefilled and surrounding edges of the substrates were bonded with epoxyseries adhesive jointly enclosing the particles, a display device wasobtained. The mixing rate of the particles A and the particles B wasdetermined to the same weight each other respectively and the fillingfactor of these particles between the glasses substrates was adjusted to60% by volume. As a gas fulfilling the remained cavities, air withrelative humidity of 50% RH was employed. The evaluation results areshown in Table K.

Example K2

The display device was assembled similarly as Example K1 except that theresin composing the particles was replaced to thermoplastic polyetherester elastomer: Hytrel5557M (available from DUPONT TORAY CO., LTD.) inExample K2. The evaluation results are shown in Table K.

Example K3

The display device was assembled similarly as Example K1 except that thefilling factor of the particles between the glass substrates was variedto 90% by volume in Example K3. The evaluation results are shown inTable K. Because the volume population of the particles was great, thecontrast turned worse a little.

Example K4

The display device was assembled similarly as Example K1 except that therelative humidity of the gas in the cavities surrounding the particleswas varied to 70% RH at 25° C. in Example K4. The evaluation results areshown in Table K. Because the humidity of the gas in the cavities washigh, durability deteriorated a little.

Comparative Example K1

The display device was assembled similarly as Example K1 except that theresin composing the particles was replaced to thermoplastic polyetherester elastomer: Hytrel3548W (available from DUPONT TORAY CO., LTD.) inComparative Example K1. The evaluation results are shown in Table K.Because the tensile elastic modulus of the resin was small and becausethe water absorption was large, degradation of durability wastremendous.

Example L1

As for particles A, 4 phr of carbon black (CB) and 2 phr of BONTRON N07(available from Orient Chemical Co., Ltd.) as charge control agent wereadded into 100 parts by mass of thermoplastic polyether ester elastomer:Hytrel5527 (available from DUPONT TORAY CO., LTD.), and after kneading,the mixture was crushed with Jetmill and classified into particles.

As for particles B, 10 phr of Titanium oxide and 2 phr of BONTRON N07(available from Orient Chemical Co., Ltd.) as charge control agent wereadded into 100 parts by mass of thermoplastic polyether ester elastomer:Hytrel5527 (available from DUPONT TORAY CO., LTD.), and after kneading,the mixture was crushed with Jetmill and classified into particles.

Between a pair of glass substrates both carrying indium oxide electrodeswith the thickness of about 500 Å respectively and adjusting thedistance with a spacer to 400 μm, the particles A and B above werefilled and surrounding edges of the substrates were bonded with epoxyseries adhesive jointly enclosing the particles, a display device wasobtained. The mixing rate of the particles A and the particles B wasdetermined to the same weight each other respectively and the fillingfactor of these particles between the glasses substrates was adjusted to60% by volume. As a gas fulfilling the remained cavities, air withrelative humidity of 50% RH was employed. The evaluation results areshown in Table L.

Example L2

The display device was assembled similarly as Example L1 except that theresin composing the particles was replaced to thermoplastic polyetherester elastomer: Hytrel2551 (available from DUPONT TORAY CO., LTD.) inExample L2. The evaluation results are shown in Table L.

Example L3

The display device was assembled similarly as Example L1 except that thefilling factor of the particles between the glass substrates was variedto 90% by volume in Example L3. The evaluation results are shown inTable L.

Example L4

The display device was assembled similarly as Example L1 except that therelative humidity of the gas in the cavities surrounding the particleswas varied to 70% RH at 25° C. in Example L4. The evaluation results areshown in Table L. Because the humidity of the gas in the cavities washigh, durability deteriorated a little.

Comparative Example L1

The display device was assembled similarly as Example L1 except that theresin composing the particles was replaced to thermoplastic polyetherester elastomer: Hytrel4057 (available from DUPONT TORAY CO., LTD.) inComparative Example L1. The evaluation results are shown in Table L.Because the tensile elastic modulus of the resin was small and becausethe water absorption was large, degradation of durability wastremendous.

Example M1

A display device was assembled as follows:

To begin with, a substrate having electrodes with partition walls wasprepared. On a glass substrate having indium oxide electrodes with athickness of about 500 Å, ribs with a height of 200 μm were made and apartition wall of stripe-shaped single rib configuration was formed.

The ribs are formed as follows: With regard to a paste, preparing aglass powder melting a mixture of SiO₂, Al₂O₃, B₂O₃ and ZnO as inorganicpowders, cooling, and crushing; and also preparing a thermosetting epoxyresin as a resin, the paste was provided by adjusting the viscosity to12000 cps with the use of a solvent.

Next, applying this paste over the entire surface of above-mentionedsubstrate, cured by heating at the temperature of 150° C., repeated theapplication and curing, the thickness (equivalent to the height of thepartition wall) was adjusted to 200 μm. Then, adhering dry photoresist,provided a mask having a partition pattern with line width of 50 μm,space of 200 μm, and pitch of 250 μm respectively, by exposure andetching. As a result, a partition wall having a predetermined stripeconfiguration was formed by removing unnecessary portions with the useof sandblast.

Further, both the particles A and the particles B were prepared. As forparticles A, blending urethane particles (average particle diameter: 5.8μm) as mother particles, carbon (average particle diameter: 0.03 μm) aschild particles and BONTRON N07 as charge control agent; and fixing thechild particles and the charge control agent over the surface of themother particles with a mechano-fusion method, they were changed intocombined particles. As for particles B, blending urethane particles(average particle diameter: 5.8 μm) as mother particles, TiO₂ (averageparticle diameter: 0.015 μm) as child particles and BONTRON E89 ascharge control agent; and fixing the child particles and the chargecontrol agent over the surface of the mother particles with amechano-fusion method, they were changed into combined particles.

Between a pair of the foregoing glass substrates both carrying indiumoxide electrodes with the thickness of about 500 Å and ribs respectivelyand adjusting the space with a spacer to 400 μm, the particles A and Babove were filled and surrounding edges of the substrates were bondedwith epoxy series adhesive jointly enclosing the particles, a displaydevice was obtained. The mixing rate of the particles A and theparticles B was determined to the same weight each other respectivelyand the filling factor of these particles between the glass substrateswas adjusted to 60% by volume. As a gas fulfilling the remainedcavities, air with relative humidity of 35% RH was employed.

The evaluation results about the particle diameters of each particle,Span of the particle diameter distribution (referred to merely “Span”below), a ratio between the particle diameter of the mother particlesand the particle diameter of the child particles, and thesolvent-indissoluble ratio of the particles, and the display capabilityof the assembled image display device are shown in Table M.

Example M2

The display device was assembled similarly as Example M1 except that thematerial for the mother particles of the particles A was replaced tocarbon microbeads ICB in Example M2. The property of each particles andthe evaluation results are shown in Table M. Because Span of theparticle diameter distribution was large, durability deteriorated alittle.

Example M3

The display device was assembled similarly as Example M1 except that thematerial for the child particles of the particles B was replaced to anacryl containing titanium oxides (TiO₂) in Example M3. The property ofeach particles and the evaluation results are shown in Table M. Becausethe particle diameter ratio between the mother particles and the childparticles of the particles B was large, the minimum driving voltageelevated a little, the initial contrast ratio and the retention felldown a little.

Example M4

The display device was assembled similarly as Example M1 except that thepartition wall was not formed in Example M4. The property of eachparticles and the evaluation results are shown in Table M. Because thepartition wall was absent, durability deteriorated a little.

Comparative Example M1

The display device was assembled similarly as Example M1 except thatBONTRON N07 was added to the material for the mother particles of theparticles A, that BONTRON E89 was added to the material for the motherparticles of the particles B and that the child particles were not usedin Comparative Example M1. The property of each particles and theevaluation results are shown in Table M. Because the child particleswere not used, the driving voltage extremely increased.

Example N1

Acidic charge control agent: BONTRON E84 (available from Orient ChemicalCo., Ltd.; salicylic acid metal complex) in an amount of 5% by weightwas dissolved in ethanol with the use of a mixer, after removingunsolved component by filtration, Perknock CFB 200W-40 (available fromDAINIPPON INK AND CHEMICALS, INCORPORATED; white urethane particles) wasadded and agitated, then, the mixed solution was filtered with filterpaper of 5C and dried at the temperature of 110° C. The measured resultsabout both the averaged particle diameter and the surface charge densityof the particle for displaying images are shown in Table N.

Example N2

The particles for displaying images were prepared similarly as ExampleN1 except that the charge control agent was replaced to BONTRON E89(available from Orient Chemical Co., Ltd.; phenolic condensate) inExample N2. The measured results about the averaged particle diameterand the surface charge density are shown in Table N.

Example N3

The particles for displaying images were prepared similarly as ExampleN1 except that the charge control agent was replaced to BONTRON N07(available from Orient Chemical Co., Ltd.; nigrosine compound) and thatthe fine particles were replaced to Perknock CFB 620C-40 (available fromDAINIPPON INK AND CHEMICALS, INCORPORATED; black urethane particles) inExample N3. The measured results about the averaged particle diameterand the surface charge density are shown in Table N.

Example N4

The particles for displaying images were prepared similarly as ExampleN1 except that the charge control agent was replaced to BONTRON N21(available from Orient Chemical Co., Ltd.; resinous acid modified azine)and that the fine particles were replaced to Perknock CFB 101-40(available from DAINIPPON INK AND CHEMICALS, INCORPORATED; clear colorurethane particles) in Example N4. The measured results about theaveraged particle diameter and the surface charge density are shown inTable N.

Comparative Example N1

The particles for displaying images were prepared similarly as ExampleN1 except that the charge control agent was not used in ComparativeExample N1. The measured results about the averaged particle diameterand the surface charge density are shown in Table N.

Example P1

As for resin coating particles A, they were prepared by using aspherical fine particles of white polymethylmethacrylate (MBX-5W,available from SEKISUI PLASTICS CO., LTD.; average particle diameter:4.3 μm), acryl urethane resin (EAU65B, available from Asia-kogyo Co.,Ltd.) as a coating resin, and IPDI series crosslinking agent(Excel-Hardner HX, available from Asia-kogyo Co., Ltd.) as acrosslinking agent. The coating method adopted Aggromaster MINI(produced by Hosokawa Micron Co., Ltd.). Spherical fine particles in anamount of 150 g were thrown into a treatment container with thetemperature maintained at 80° C., and while rotating an agitation bladewith the speed of 600 rpm, they were flowed intensely induced by theintroduction of compressed air with the temperature of 80° C. from thebottom part of the treatment container. The above-mentioned acrylurethane resin and crosslinking agent were dissolved in MEK solvent andthe solution was sprayed in a misty way from a spray gun for about 30minutes. After the termination of the spraying, they were further driedfor 10 minutes and the resin coating particles A were prepared. Theaverage particle diameter and the variation rate of particle diameter ofthe resin coating particles A were 7.2 μm, and R=1.67 respectively.

As for resin coating particles B, they were prepared by using sphericalfine particles of black polymethylmethacrylate (MBX-5B, available fromSEKISUI PLASTICS CO., LTD.; average particle diameter: 5.6 μm) andfluorocarbon polymers (Kyner2751, available from Elph Atochem Japan Co.,Ltd) as coating resin. The coating method was the same as particles A.

The average particle diameter and the variation rate of particlediameter of the resin coating particles B were 7.6 μm, and R=1.36respectively.

Next, the display device was assembled as follows: Namely, between apair of glass substrates both carrying indium oxide electrodes with thethickness of about 500 Å respectively and adjusting the distance with aspacer to 200 μm, the particles A and B above were filled andsurrounding edges of the substrates were bonded with epoxy seriesadhesive jointly enclosing the particles, a display device was obtained.The mixing rate of the particles A and the particles B was determined tothe same weight each other respectively and the filling factor of theseparticles between the glasses substrates was adjusted to 60% by volume.The evaluation results about the property of each particles and thedisplay capability are shown in Table P.

Example P2

The display device was assembled similarly as Example P1 except that theresin for coating the resin coating particles A was replaced to nylonresin TORESIN EF300 (available from Teikoku Chemical Industry Co., Ltd.)in Example P2. The evaluation results about the property of eachparticles and the display capability are shown in Table P.

Example P3

The display device was assembled similarly as Example P1 except that 2phr of charge control agent BONTRON P51 (available from Orient ChemicalCo., Ltd.) was added to the resin for coating the resin coatingparticles A in Example P3. The evaluation results about the property ofeach particles and the display capability are shown in Table P. Becausethe charge control agent was added, the contrast turned better a little.

Example P4

The display device was assembled similarly as Example P1 except that theatomization condition of coating was adjusted and the amount of thecoating resin was increased in the preparation of resin coatingparticles A. The evaluation results about the property of each particlesand the display capability are shown in Table P. Because the amount ofthe coating resin was too much, the retention factor decreased a little.

Example P5

The display device was assembled similarly as Example P1 except that theresin for coating the resin coating particles A was only acryl urethaneresin (EAU65B, available from Asia-kogyo Co., Ltd.) in Example P5. Theevaluation results about the property of each particles and the displaycapability are shown in Table P. Because the crosslinking agent was notused, a tremendous degradation occured during storage.

Comparative Example P1

The display device was assembled similarly as Example P1 except thatboth the particles A and the particles B were used bare without coatingresin in Comparative Example P1. The evaluation results about theproperty of each particles and the display capability are shown in TableP.

Example Q1

PMMA particles (MBX-8, available from SEKISUI PLASTICS CO., LTD.) withaverage particle diameter of 5.6 μm were employed as central sphericalparticles, which were previously prepared by polymerization of styrenemonomer with AIBN (azo bis iso butyronitrile) among toluene resulting inresin component of number average molecular weight of 20 thousand. Thefourth grade ammonium salt-based compound was dissolved as chargecontrol agent in an amount of 0.12 g to 100 g of styrenic resinous paintcontaining 2.5% by weight of resin component, dispersing 5 g of theforegoing central spherical particles, after drying them with spraydryer, positively charged particles of 5-10 μm were obtained with theuse of grinding classifier (FM -120, produced by Japan Pnewmatic Co.,Ltd.). A cross-sectional observation about the resulted particles withthe use of scanning electron microscope recognized that an outer layerwith the thickness of 0.6 to 0.9 μm was formed. Further, the surfacecharge density of the particles was +42 μC/m² and the maximum value ofsurface potential at 0.3 second after the surface potential measurementwas 460 V.

Index of refraction of PMMA simple substance as the center particles was1.49, and index of refraction of styrene resin was 1.60.

A black polymerization toner (spherical particles with average particlediameter of 8 μm, surface charge density: −50 μC/m², the maximum valueof surface potential at 0.3 second after the surface potentialmeasurement: 450 V) for electrophotography was employed as the negativecharged particles.

For the purpose of charging the particles, an equivalent amount of bothparticles were mixed and agitated and frictional charging was conducted.

Among a cell made by connecting a glass substrate whose inside was ITOtreated and another copper substrate deployed with a spacer of 200 μm,the mixed particles above were filled by the cavity factor of 70%, adisplay device was obtained.

The ITO glass substrate and the copper substrate were connected to apower source respectively, and when DC voltage of 250 V was applied in amanner that the former corresponds to a negative electrode and thelatter corresponds to positive electrode, positively charged particlesflew to the negative electrode and negatively charged particles flew tothe positive electrode. As a result, the display device observed throughthe glass substrate displayed white. Then, when the polarity of appliedvoltage was reversed, the particles flew to the counter electrodesrespectively, and the display device displayed black.

The response time for the applied voltage was measured to be 1 msec.Even after leaving the display device discontinuing the applied voltagefor one day, each display was maintained.

Further, although the polarity of the applied voltage was reversedrepeatedly for 10,000 times, there was almost no variation of theresponse speed.

Example R1

The fourth grade ammonium salt-based compound was kneaded as chargecontrol agent into PMMA resin with the use of a Plasto mill, then,crushing into powders with the use of a Coffee mill, indefiniteparticles of 5-10 μm were obtained with the use of grinding classifier(FM-120, produced by Japan Pnewmatic Co., Ltd.).

A styrene monomer in an amount of 70 parts by weight, AIBN (azo bis isobutyronitrile) in an amount of 0.5 part by weight, and the fourth gradeammonium salt-based compound as charge control agent in an amount of 5parts by weight were added to 30 parts by weight of the indefiniteparticles, and they were mixed. The mixed solution was dispersed in 0.5%surfactant (lauryl sodium sulfate) aqueous solution of a quantity of 10times, and they were suspended and polymerized, and after filtering anddrying them, positively charged particles of 5-10 μm were obtained withthe use of grinding classifier (FM-120, produced by Japan Pnewmatic Co.,Ltd.). The surface charge density of the particles was +43 μC/m² and themaximum value of surface potential at 0.3 second after the surfacepotential measurement was 450 V. Index of refraction of PMMA simplesubstance as the indefinite particle was 1.49, and index of refractionof styrene resin was 1.60.

A black polymerization toner (spherical particles with average particlediameter of 8 μm, surface charge density: −50 μC/m², maximum value ofsurface potential at 0.3 second after the surface potential measurement:450 V) for electrophotography was employed as the negative chargedparticles.

For the purpose of charging the particles, an equivalent amount of bothparticles were mixed and agitated and frictional charging was conducted.

Among a cell made by connecting a glass substrate whose inside was ITOtreated and another copper substrate deployed with a spacer of 200 μm,the mixed particles above were filled by the cavity factor of 70%, adisplay device was obtained. The ITO glass substrate and the coppersubstrate were connected to a power source respectively, and when DCvoltage of 250 V was applied in a manner that the former corresponds toa negative electrode and the latter corresponds to positive electrode,positively charged particles flew to the negative electrode andnegatively charged particles flew to the positive electrode. As aresult, the display device observed through the glass substratedisplayed white. Then, when the polarity of applied voltage wasreversed, the particles flew to the counter electrodes respectively, andthe display device displayed black.

The response time for the applied voltage was measured to be 1 msec.Even after leaving the display device discontinuing the applied voltagefor one day, each display was maintained.

Further, although the polarity of the applied voltage was reversedrepeatedly for 10,000 times, there was almost no variation of theresponse speed.

Example S1

As a preparation of the positively charged particles, AIBN (azo bis isobutyronitrile) in an amount of 0.5 part by weight was dissolved in 80part by weight of methyl methacrylate monomer and 20 part by weight ofmethacrylic acid 2-(dimethylamino)ethyl monomer, and 20 part by weightof the lipophilicated titanium oxide by coupling treatment wasdispersed. The mixed solution was dispersed in 0.5% surfactant (laurylsodium sulfate) aqueous solution of a quantity of 10 times, and theywere suspended and polymerized, and after filtering and drying them,white particles of 5 to 10 μm were obtained with the use of grindingclassifier (FM-120, produced by Japan Pnewmatic Co., Ltd.). The surfacecharge density of the particles was +44 μC/m² and the maximum value ofsurface potential at 0.3 second after the surface potential measurementwas 410 V.

As a preparation of the negatively charged particles, AIBN (azo bis isobutyronitrile) in an amount of 0.5 part by weight and metal-containingazo compound as dye in an amount of 5 part by weight were dissolved instyrene monomer. The mixed solution was dispersed in 0.5% surfactant(lauryl sodium sulfate) aqueous solution of a quantity of 10 times, andthey were suspended and polymerized, and after filtering and dryingthem, black particles of 5 to 10 μm were obtained with the use ofgrinding classifier (FM-120, produced by Japan Pnewmatic Co., Ltd.). Thesurface charge density of the particles was −40 μC/m² and the maximumvalue of surface potential at 0.3 second after the surface potentialmeasurement was 480 V. For the purpose of charging the particles, anequivalent amount of both particles were mixed and agitated andfrictional charging was conducted.

Among a cell made by connecting a glass substrate whose inside was ITOtreated and another copper substrate deployed with a spacer of 200 μm,the mixed particles above were filled by the cavity factor of 70%, adisplay device was obtained.

The ITO glass substrate and the copper substrate were connected to apower source respectively, and when DC voltage of 250 V was applied in amanner that the former corresponds to a negative electrode and thelatter corresponds to positive electrode, positively charged particlesflew to the negative electrode and negatively charged particles flew tothe positive electrode. As a result, the display device observed throughthe glass substrate displayed white. Then, when the polarity of appliedvoltage was reversed, the particles flew to the counter electrodesrespectively, and the display device displayed black.

The response time for the applied voltage was measured to be 1 msec.Even after leaving the display device discontinuing the applied voltagefor one day, each display was maintained.

Further, although the polarity of the applied voltage was reversedrepeatedly for 10,000 times, there was almost no variation of theresponse speed.

Example T1

As for particles A, charge control agent: BONTRON E84 (available fromOrient Chemical Co., Ltd.; salicylic acid metal complex) in an amount of5% by weight was dissolved in ethanol with the use of a mixer, afterremoving unsolved component by filtration, Perknock CFB200W-40(available from DAINIPPON INK AND CHEMICALS, INCORPORATED; whiteurethane particles) was added and agitated, then, the mixed solution wasfiltered with filter paper of 5C and dried at the temperature of 110° C.

As for particles B, charge control agent: BONTRON N9 (available fromOrient Chemical Co., Ltd.) in an amount of 5% by weight was dissolved inethanol with the use of a mixer, after removing unsolved component byfiltration, Perknock CFB 620C-40 (available from DAINIPPON INK ANDCHEMICALS, INCORPORATED; black urethane particles) was added andagitated, then, the mixed solution was filtered with filter paper of 5Cand dried at the temperature of 110° C.

Next, the display device was assembled as follows: Namely, between apair of glass substrates both carrying indium oxide electrodes with thethickness of about 500 Å respectively and adjusting the distance with aspacer to 400 μm, the particles A and B above were filled andsurrounding edges of the substrates were bonded with epoxy seriesadhesive jointly enclosing the particles, a display device was obtained.The mixing rate of the particles A and the particles B was determined tothe same weight each other respectively and the filling factor of theseparticles between the glasses substrates was adjusted to 60% by volume.

The evaluation results about the property of each particles and thedisplay capability are shown in Table T.

Example T2

The particles and the display device were prepared similarly as ExampleT1 except that the charge control agent for the particles B was replacedto aminosilane coupling agent (A1120; available from Nippon Unicar Co.,Ltd) in Example T2. The evaluation results about the property of eachparticles and the display capability are shown in Table T.

Example T3

The particles and the display device were prepared similarly as ExampleT1 except that the charge control agent for the particles A was not usedin Example T3. The evaluation results about the property of eachparticles and the display capability are shown in Table T.

Comparative Example T1

The particles and the display device were prepared similarly as ExampleT2 except that the charge control agent for the particles A was not usedin Comparative Example T1. The evaluation results about the property ofeach particles and the display capability are shown in Table T.

TABLE A Example A1 Example A2 Example A3 Example A4 (Particles A)Particles to be coated Black toner Black toner Black toner Black tonerCoating resin EAU65B/HX TORESIN/EF300 EAU65B/HX EAU65B/HX Amount ofcoating 4 5 4 38 resin-1(%) Charged potential of 8 10 8 8 resin (V)Solvent-indissoluble 92 89 92 92 ratio of resin (%) Additive BONTRON P51(Particles B) Particles to be coated Yellow toner Yellow toner Yellowtoner Yellow toner Coating resin Kyner2751 Kyner2751 Kyner2751 Kyner2751Amount of coating 3 3 3 3 resin-1(%) Charged potential of 23 23 23 23resin (V) Solvent-indissoluble 88 88 88 88 ratio of resin (%)(Evaluation of display capability −1) Initial contrast ratio (i) 7.8 7.08.9 8.0 After 10000 times Contrast ratio (ii) 7.3 6.6 8.2 7.2 Retention% ((ii)/(i)) 94 94 92 92 After leaving 5 days Contrast ratio (iii) 7.26.5 8.0 6.9 Retention % 92 92 89 86 ((iii)/(i)) Comp. Ex. Example A5Example A6 A1 (Particles A) Particles to be coated Black toner Blacktoner Black toner Coating resin ARE6071/ EAU65B Nothing Sumicure MAmount of coating 6 4 resin-1(%) Charged potential of 330 8 resin (V)Solvent-indissoluble 88 48 ratio of resin (%) Additive (Particles B)Particles to be coated Yellow toner Yellow toner Yellow toner Coatingresin Kyner2751 Kyner2751 Kyner2751 Amount of coating 3 3 resin-1(%)Charged potential of 23 23 resin (V) Solvent-indissoluble 88 88 ratio ofresin (%) (Evaluation of display capability −1) Initial contrast 7.8 7.87.1 ratio (i) After 10000 times Contrast ratio (ii) 5.9 7 3.9 Retention% ((ii)/(i)) 76 90 55 After leaving 5 days Contrast ratio (iii) 5.0 4.83.0 Retention % ((iii)/(i)) 64 61 42

TABLE B Example B1 Example B2 Example B3 (Particles A) Particles Blacktoner Black toner Carbon Micro Beads PC Span 0.74 1.23 2.72 AverageParticle Diameter (i) (μm) 7.0 9.2 12.5 Solvent-indissoluble ratio (%)8.9 89 87 (Particles B) Particles Yellow toner Yellow toner Yellow TonerSpan 0.66 0.66 0.66 Average Particle Diameter (ii) (μm) 9.1 9.1 9.1Solvent-indissoluble ratio (%) 92 92 92 Particle Diameter ratio((ii)/(i)) 1.3 1 1.4 (Evaluation of display capability −2) InitialContrast ratio (iii) 7.1 6.9 7.2 After 1000 times Contrast ratio (iv)6.6 6.2 6.6 Retention ((iv)/(iii)) 93 90 92 After leaving 5 daysContrast ratio (vi) 6.5 6.1 6.3 Retention ((vi)/(iii)) 92 88 87 ExampleB4 Example B5 Comp. Ex. B1 (Particles A) Particles AER6071/Carbon CarbonMicro Beads Carbon Micro MSB Beads ICB Span 4.8 4.9 8.4 Average ParticleDiameter (i)(μm) 19.2 62.8 471.4 Solvent-indissoluble ratio (%) 49 87 87(Particles B) Particles Yellow toner Yellow toner Yellow toner Span 0.660.66 0.66 Average Particle Diameter (ii)(μm) 9.1 9.1 9.1Solvent-indissoluble ratio (%) 92 92 92 Particle Diameter ratio((ii)/(i)) 2.1 6.87 51.6 (Evaluation of display capability −2) InitialContrast ratio (iii) 6.9 5.0 4.3 After 1000 times Contrast ratio (iv)6.0 3.5 2.15 Retention ((iv)/(iii)) 87 70 50 After leaving 5 daysContrast ratio (vi) 4.21 3.4 1.76 Retention ((vi)/(iii)) 61 68 41

TABLE C Example C1 Example C2 (Particles A) Resin material EAU206B/HXEAU205B/HX Aditive CB/BONTRON N07 CB/BONTRON N07 (Particles B) Resinmaterial EAU206B/HX EAU205B/HX Aditive TiO₂/BONTRON E89 TiO₂/BONTRON E89Surface Potential of Resin (V) 405 380 Solvent-indissoluble ratio ofresin (%) 92 89 (Evaluation of display capability −3) Reflection Densityat 10 times (i) 1.8 1.7 Reflection Density after leaving 10 1.6 1.5 days(ii) Retention ((ii)/(i), %) 92 88 Example C3 Comp. Ex. C1 (Particles A)Resin material EAU206B EAU188B/HX Additive CB/BONTRON N07 CB/BONTRON N07(Particles B) Resin material EAU206B EAU188B/HX Additive TiO₂/BONTRONE89 TiO₂/BONTRON E89 Surface Potential of Resin (V) 405 156Solvent-indissoluble ratio of resin (%) 48 90 (Evaluation of displaycapability −3) Reflection Density at 10 times (i) 1.7 1.7 ReflectionDensity after leaving 10 1.4 0.6 days (ii) Retention ((ii)/(i), %) 82 35

TABLE D Example D1 Example D2 Example D3 (Particles A) Resin materialEAU204B/HX EAU203B/HX EAU204B/HX Additive CB/BONTRON N07 CB/BONTRON N07CB/BONTRON N07 Surface Potential (V) 430 305 430 Solvent-indissoluble 9086 90 ratio of resin (%) (Particles B) Resin material EAU204B/HXEAU203B/HX EAU203B/HX Additive TiO₂/BONTRON E89 TiO₂/BONTRON E89TiO₂/BONTRON E89 Surface Potential (V) 400 320 320 Solvent-indissoluble90 87 87 ratio of resin (%) Surface Potential 30 15 110 Difference (V)between Particles A and Particles B (Evaluation of display capability−3) Reflection Density at 1.90 1.75 1.69 10 times (i) Reflection Densityafter 1.73 1.54 1.35 leaving 10 days (ii) Retention ((ii)/(i), %) 91 8880 Example D4 Comp. Ex. D1 (Particles A) Resin material EAU204BEAU53B/HX Additive CB/BONTRON N07 CB/BONTRON N07 Surface Potential (V)410 60 Solvent-indissoluble ratio of resin (%) 48 87 (Particles B) Resinmaterial EAU204B EAU188B/HX Additive TiO₂/BONTRON E89 TiO₂/BONTRON E89Surface Potential (V) 390 75 Solvent-indissoluble ratio of resin (%) 4887 Surface Potential Difference (V) 30 15 between Particles A andParticles B (Evaluation of display capability −3) Reflection Density at10 times (i) 1.89 1.7 Reflection Density after leaving 10 days (ii) 1.660.61 Retention ((ii)/(i), %) 88 36

TABLE E Example E1 Example E2 Ref. Example E1 (Particles A) Resinmaterial Hytrel7247 Hytrel5557 Hytrel7247 Additive CB/BONTRON N07CB/BONTRON N07 CB/BONTRON N07 (Particles B) Resin material Hytrel7247Hytrel5557 Hytrel7247 Additive TiO₂/BONTRON E89 TiO₂/BONTRON E89TiO₂/BONTRON E89 Surface Hardness 75 58 75 (deg.) of resin at 0° C.Surface Hardness 71 55 71 (deg.) of resin at 25° C. Surface Hardness 6144 61 (deg.) of resin at 100° C. Surface Hardness at 1.23 1.32 1.23 0°C./Surface Hardness at 100° C. Volume Population 60 60 90 (%) ofParticle Water-absorption 0.3 0.4 0.3 (%) of resin Solvent-indissoluble92 93 92 ratio (%) of resin (Evaluation of display capability −4)Contrast ratio at 8.22 8.18 6.20 0° C. Contrast ratio at 8.19 8.11 6.1525° C. Contrast ratio at 7.99 7.88 6.02 60° C. Comp. Ex. E1 Comp. Ex. E2(Particles A) Resin material Hytrel4057 TORESIN EF300 AdditiveCB/BONTRON CB/BONTRON N07 N07 (Particles B) Resin material Hytrel4057TORESIN EF300 Additive TiO₂/ TiO₂/ BONTRON E89 BONTRON E89 SurfaceHardness (deg.) of 44 41 resin at 0° C. Surface Hardness (deg.) of 39 31resin at 25° C. Surface Hardness (deg.) of 25 16 resin at 100° C.Surface Hardness at 0° C./ 1.76 2.63 Surface Hardness at 100° C. VolumePopulation (%) of 60 60 Particle Water-absorption (%) of 0.8 5.3 resinSolvent-indissoluble ratio 93 86 (%) of resin (Evaluation of displaycapability −4) Contrast ratio at 0° C. 8.16 8.00 Contrast ratio at 25°C. 8.01 7.99 Contrast ratio at 60° C. 3.84 2.55

TABLE F Example F1 Example F2 Ref. Example F1 (Particles A) Resinmaterial Hytrel2751 Hytrel2571 Hytrel2751 Additive CB/BONTRON N07CB/BONTRON N07 CB/BONTRON N07 (Particles B) Resin material Hytrel2751Hytrel2571 Hytrel2751 Additive TiO₂/BONTRON E89 TiO₂/BONTRON E89TiO₂/BONTRON E89 Tensile break 35.0 29.0 35.0 strength (Mpa) of resinVolume Population 60 60 90 (%) of Particle Water-absorption 0.2 0.2 0.2(%) of resin Solvent-indissoluble 91 92 91 ratio (%) of resin(Evaluation of display capability −5) Initial Contrast 8.22 8.12 6.50ratio Contrast ratio after 7.41(90%) 7.15(88%) 5.91(91%) 10000 times(Retention) Comp. Ex. F1 Comp.Ex. F2 (Particles A) Resin materialHytrel4047 Hytrel3548 Additive CB/BONTRON N07 CB/BONTRON N07 (ParticlesB) Resin material Hytrel4047 Hytrel3548 Additive TiO₂/BONTRON E89TiO₂/BONTRON E89 Tensile break strength (Mpa) of resin 19.3 11.5 VolumePopulation (%) of Particle 60 60 Water-absorption (%) of resin 0.8 3.6Solvent-indissoluble ratio (%) of resin 92 92 (Evaluation of displaycapability −5) Initial Contrast ratio 8.23 8.01 Contrast ratio after10000 times 5.02(61%) 4.24(53%) (Retention)

TABLE G Example G1 Example G2 Ref. Example. G1 (Particles A) Resinmaterial Hytrel6347 Hytrel6347M Hytrel6347 Additive CB/BONTRON N07CB/BONTRON N07 CB/BONTRON N07 (Particles B) Resin material Hytrel6347Hytrel6347M Hytrel6347 Additive TiO₂/BONTRON E89 TiO₂/BONTRON E89TiO₂/BONTRON E89 Izod Impact Strength 240 130 240 (with Notch) (J/m) ofresin Volume Population (%) 60 60 90 of Particle Water-absorption (%)0.4 0.4 0.4 of resin Solvent-indissoluble 93 92 93 ratio (%) of resin(Evaluation of display capability −5) Initial Contrast ratio 8.20 8.096.40 Contrast ratio after 7.46(91%) 7.04(87%) 5.70(89%) 10000 times(Retention) Comp. Ex. G1 Comp. Ex. G2 (Particles A) Resin materialHytrel7247M Hytrel7247F Additive CB/BONTRON N07 CB/BONTRON N07(Particles B) Resin material Hytrel7247M Hytrel7247F AdditiveTiO₂/BONTRON E89 TiO₂/BONTRON E89 Izod Impact Strength 90 50 (withNotch) (J/m) of resin Volume Population (%) 60 60 of ParticleWater-absorption (%) of 0.3 0.2 resin Solvent-indissoluble 92 92 ratio(%) of resin (Evaluation of display capability −5) Initial Contrastratio 8.19 8.15 Contrast ratio after 4.83(59%) 3.91(48%) 10000 times(Retention)

TABLE H Example H1 Example H2 Ref. Example H1 (Particles A) Resinmaterial Hytrel7247L-01 Hytrel6347L-01 Hytrel7247L-01 AdditiveCB/BONTRON N07 CB/BONTRON N07 CB/BONTRON N07 (Particles B) Resinmaterial Hytrel7247L-01 Hytrel6347L-01 Hytrel7247L-01 AdditiveTiO₂/BONTRON E89 TiO₂/BONTRON E89 TiO₂/BONTRON E89 Abrasion loss (Taber)8.1 9.2 8.1 (mg) Volume Population 60 60 90 (%) of ParticleWater-absorption 0.3 0.3 0.3 (%) of resin Solvent-indissoluble 93 91 93ratio (%) of resin (Evaluation of display capability −5) InitialContrast ratio 8.25 8.22 6.11 Contrast ratio after 7.51(91%) 7.23(88%)5.25(86%) 10000 times (Retention) Comp. Ex. H1 Comp. Ex. H2 (ParticlesA) Resin material Hytrel6347G10 TORESINEF300 Additive CB/BONTRON N07CB/BONTRON N07 (Particles B) Resin material Hytrel6347G10 TORESIN EF300Additive TiO₂/BONTRON E89 TiO₂/BONTRON E89 Abrasion loss (Taber) 28.232.9 (mg) Volume Population (%) 60 60 of Particle Water-absorption (%)of 0.3 5.3 resin Solvent-indissoluble 92 86 ratio (%) of resin(Evaluation of display capability −5) Initial Contrast ratio 8.14 7.88Contrast ratio after 3.91(48%) 2.44(31%) 10000 times (Retention)

TABLE J Example J1 Example J2 Example J3 (Particles A) Resin Hytrel5077Hytrel4777 Hytrel5077 Additive CB/BONTRON N07 CB/BONTRON N07 CB/BONTRONN07 (Particles B) Resin Hytrel5077 Hytrel4777 Hytrel5077 AdditiveTiO₂/BONTRON E89 TiO₂/BONTRON E89 TiO₂/BONTRON E89 Volume Population (%)60 60 90 of Particle Relative Humidity (% 50 50 50 RH) of Air incavities (Physical Property evaluation of resin) Tensile Elastic Modulus84.4 56.4 84.4 (Mpa) Water absorption (% by 0.6 0.7 0.6 weight)Solvent-indissoluble 91 92 91 ratio of resin (%) (Evaluation of displaycapability −5) Initial Contrast ratio (i) 8.20 8.11 6.4 Contrast ratio(ii) after 7.38 7.06 5.71 10000 times repetition Retention ((ii)/(i), %)90 87 89 Example J4 Comp. Ex. J1 (Particles A) Resin Hytrel5077Hytrel3548W Additive CB/BONTRON N07 CB/BONTRON N07 (Particles B) ResinHytrel5077 Hytrel3548W Additive TiO₂/BONTRON E89 TiO₂/BONTRON E89 VolumePopulation (%) 60 60 of Particle Relative Humidity (% RH) 70 50 of Airin cavities (Physical Property evaluation of resin) Tensile ElasticModulus 84.4 21.3 (Mpa) Water absorption (% by 0.6 3.6 weight)Solvent-indissoluble ratio 91 92 of resin (%) (Evaluation of displaycapability −5) Initial Contrast ratio (i) 8.18 8.0 Contrast ratio (ii)after 6.71 4.24 10000 times repetition Retention ((ii)/(i), %) 82 51

TABLE K Example K1 Example K2 Example K3 (Particles A) Resin Hytrel6377Hytrel5557M Hytrel6377 Additive CB/BONTRON N07 CB/BONTRON N07 CB/BONTRONN07 (Particles B) Resin Hytrel6377 Hytrel5557M Hytrel6377 AdditiveTiO₂/BONTRON E89 TiO₂/BONTRON E89 TiO₂/BONTRON E89 Volume Population (%)60 60 90 of Particle Relative Humidity (% 50 50 50 RH) of Air incavities (Physical Property evaluation of resin) Tensile Elastic 355 236355 Modulus (Mpa) Water absorption (% 0.4 0.4 0.4 by weight)Solvent-indissoluble 91 92 91 ratio of resin (%) (Evaluation of displaycapability −5) Initial Contrast ratio 8.23 8.20 6.4 (i) Contrast ratio(ii) 7.49 7.22 5.73 after 10000 times repetition Retention ((ii)/(i), %)91 88 89 Example K4 Comp. Ex. K1 (Particles A) Resin Hytrel6377Hytrel3548W Additive CB/BONTRON CB/BONTRON N07 N07 (Particles B) ResinHytrel6377 Hytrel3548W Additive TiO₂/ TiO₂/ BONTRON E89 BONTRON E89Volume Population (%) 60 60 of Particle Relative Humidity (% 70 50 RH)of Air in cavities (Physical Property evaluation of resin) TensileElastic Modulus 355 402 (Mpa) Water absorption (% by 0.4 3.6 weight)Solvent-indissoluble 91 92 ratio of resin (%) (Evaluation of displaycapability −5) Initial Contrast ratio (i) 8.20 8.00 Contrast ratio (ii)after 6.56 4.16 10000 times repetition Retention ((ii)/(i), %) 80 52

TABLE L Example L1 Example L2 Example L3 (Particles A) Resin Hytrel5527Hytrel2551 Hytrel5527 Additive CB/BONTRON N07 CB/BONTRON N07 CB/BONTRONN07 (Particles B) Resin Hytrel5527 Hytrel2551 Hytrel5527 AdditiveTiO₂/BONTRON E89 TiO₂/BONTRON E89 TiO₂/BONTRON E89 Volume Population 6060 90 (%) of Particle Relative Humidity (% 50 50 50 RH) of Air incavities (Physical Property evaluation of resin) Tear Strength 232 216232 (kg/cm) Water absorption (% 0.4 0.6 0.4 by weight)Solvent-indissoluble 91 92 91 ratio of resin (%) (Evaluation of displaycapability −5) Initial Contrast ratio 8.18 8.10 6.4 (i) Contrast ratio(ii) 7.28 6.97 5.62 after 10000 times repetition Retention 89 86 88((ii)/(i), %) Example L4 Comp. Ex. L1 (Particles A) Resin Hytrel5527Hytrel4057 Additive CB/ CB/ BONTRON N07 BONTRON N07 (Particles B) ResinHytrel5527 Hytrel4057 Additive TiO₂/BONTRON E89 TiO₂/BONTRON E89 VolumePopulation (%) of 60 60 Particle Relative Humidity (% RH) 70 50 of Airin cavities (Physical Property evaluation of resin) Tear Strength(kg/cm) 232 95 Water absorption (% by 0.4 0.8 weight)Solvent-indissoluble ratio 91 92 of resin (%) (Evaluation of displaycapability −5) Initial Contrast ratio (i) 8.15 8.00 Contrast ratio (ii)after 6.56 4.00 10000 times repetition Retention ((ii)/(i), %) 80 50

TABLE M Example M1 Example M2 Example M3 (Particles A) Mother particles,material Urethane Carbon micro Urethane beads (Charge control agent)Particle diameter (M)(μm) 5.8 471.4 5.8 Span 1.8 8.4 1.8 Childparticles, material Carbon Carbon Carbon (Charge control agent) BONTRONNO7 BONTRON NO7 BONTRON NO7 Particle diameter (C)(μm) 0.03 0.03 0.03Particle diameter ratio (M/C) 193 1571 193 Solvent-indissoluble ratio of90 89 90 particles (%) (Particles B) Mother particles, material UrethaneUrethane Urethane (Charge control agent) Particle diameter (M)(μm) 5.85.8 5.8 Span 1.8 1.8 1.8 Child particles, material TiO₂ TiO₂ TiO₂(Charge control agent) BONTRON E89 BONTRON E89 BONTRON E89 Particlediameter (C)(μm) 0.015 0.015 0.3 Particle diameter ratio (M/C) 386 38619 Solvent-indissoluble ratio of 92 92 86 particles (%) Compoundingmethod of particles Mechano-fusion Mechano-fusion Mechano-fusionRelative humidity (% RH) of air in 35 35 35 cavities Presence or Absenceof partition Present Present Present wall (Evaluation of displaycapability −6) The Minimum driving voltage (V) 22 29 9.5 Initialcontrast ratio 7.3 7.11 6.9 Contrast ratio after 10000 times 6.42(88%)5.40(76%) 5.31(77%) (retention) Contrast ratio after leaving 5 days6.13(84%) 5.18(73%) 4.83(70%) (retention) Example M4 Comp. Ex. M1(Particles A) Mother particles, material Urethane Urethane (Chargecontrol agent) BONTRON NO7 Particle diameter (M)(μm) 5.8 5.8 Span 1.81.8 Child particles, material Carbon Nothing (Charge control agent)BONTRON NO7 Particle diameter (C)(μm) 0.03 Particle diameter ratio (M/C)193 Solvent-indissoluble ratio of 90 particles (%) (Particles B) Motherparticles, material Urethane Urethane (Charge control agent) BONTRON E89Particle diameter (M)(μm) 5.8 5.8 Span 1.8 1.8 Child particles, materialTiO₂ Nothing (Charge control agent) BONTRON E89 Particle diameter(C)(μm) 0.015 Particle diameter ratio (M/C) 386 386 Solvent-indissolubleratio of 92 92 particles (%) Compounding method of particles Mechano-Nothing fusion Relative humidity (% RH) of air 35 35 in cavitiesPresence or Absence of partition Absent Present wall (Evaluation ofdisplay capability −6) The Minimum driving voltage (V) 22 220 Initialcontrast ratio 7.2 7.9 Contrast ratio after 10000 times 6.05(84%)6.95(88%) (retention) Contrast ratio after leaving 5.76(80%) 6.56(83%) 5days (retention)

TABLE N Example N1 Example N2 Example N3 Fine particles CFB200W-40CFB200W-40 CFB620-40 Charge control agent BONTRON E84 BONTRON E89BONTRON N07 Color White White Black Average particle diameter (μm) 8.28.2 8.2 Surface charge density (μC/m²) −15 −21 16 Example N4 Comp. EX.N1 Fine particles CFB101-40 CFB200W-40 Charge control agent BONTRON N21Color Black White Average particle diameter (μm) 8.2 8.2 Surface chargedensity (μm/m²) 35 −3

TABLE P Example P1 Example P2 Example P3 (Particles A) Nuclear particlesMBX-5W MBX-5W MBX-5W Coating resin material EAU65B EF300 EAU65BCross-linking agent HX HX HX Charge control agent BONTRON P51 Amount ofcoating 4 5 4 resin −2(%) Changing ratio of particle 1.67 1.82 1.73diameter (%) Solvent-indissoluble ratio 92 89 92 of particles (%)(Particles B) Nuclear particles MBX-5B MBX-5B MBX-5B Coating resinmaterial Kyner2751 Kyner2751 Kyner2751 Amount of coating 3 3 3 resin−2(%) Changing ratio of particle 1.36 1.36 1.36 diameter (%)Solvent-indissoluble ratio 88 88 88 of particles (%) (Evaluation ofdisplay capability −7) Contrast ratio (retention) Initial 7.8 7.0 8.9After 10000 times 7.9(94) 6.6(94) 8.2(92) After leaving 5 days 7.2(92)6.5(92) 8.0(89) Comp. Example P4 Example P5 Example P1 (Particles A)Nuclear particles MBX-5W MBX-5W MBX-5W Coating resin material EAU65BEAU65B Cross-linking agent HX Charge control agent Amount of coating 384 resin −2(%) Changing ratio of 3.56 1.70 particle diameter (%)Solvent-indissoluble 92 48 ratio of particles (%) (Particles B) Nuclearparticles MBX-5B MBX-5B MBX-5B Coating resin material Kyner2751Kyner2751 Amount of coating 3 3 resin −2 (%) Changing ratio of 1.36 1.36particle diameter (%) Solvent-indissoluble 88 88 ratio of particles (%)(Evaluation of display capability −7) Contrast ratio (retention) Initial8.0 7.8 7.1 After 10000 times 7.2(90) 7.0(90) 3.9(55) After leaving 5days 6.9(86) 4.8(61) 3.0(42)

TABLE T Example T1 Example T2 (Particles A) Material CFB200W-40CFB200W-40 Surface treatment BONTRON E89 BONTRON E89 Color White WhiteParticle diameter (μm) 14.6 14.6 Surface charge density (μC/m²) −38.1−38.1 (Particles B) Material CFB620-C CFB620-C Surface treatment BONTRONN21 A1120 Color Black Black Particle diameter (μm) 13.6 13.6 Surfacecharge density (μC/m²) 36.1 10.7 Difference of Surface charge 74.2 48.8density (μC/m²) (Evaluation of display capability −8) Image density Whenentirely displaying white (A) 0.15 0.15 When entirely displaying black(B) 1.3 1.24 Contrast ratio (B/A) 8.6 8.3 Unevenness while entirely A Adisplaying Example T3 Comp. Example T1 (Particles A) Material CFB200W-40CFB200W-40 Surface treatment Color White White Particle diameter (μm)14.6 14.6 Surface charge density −0.2 −0.2 (μC/m²) (Particles B)Material CFB620-C CFB620-C Surface treatment BONTRON N21 A1120 ColorBlack Black Particle diameter (μm) 13.6 13.6 Surface charge density 36.110.7 (μC/m²) Difference of Surface 36.3 10.9 charge density (μC/m²)(Evaluation of display capability −8) Image density When entirelydisplaying 0.23 0.34 white (A) When entirely displaying 1.3 1.05 black(B) Contrast ratio (B/A) 5.7 3.1 Unevenness while A~B C entirelydisplaying

INDUSTRIAL APPLICABILITY

In accordance with the present invention, the following effects will beobtained.

-   (i) By preparing the ingredients for the particles coated with    resin, image display devices should be schemed for elevated    capability and durability should be improved.-   (ii) By preparing the ingredients for the particles with a small    Span of the particle diameter distribution, an image with a great    contrast ratio should be obtained and durability should be improved.-   (iii) By preparing the ingredients for the particles with slow    charge attenuation, an image display device superior in stability    and, particularly, in memory characteristic should be obtained.-   (iv) By preparing the ingredients for the particles regulating the    ratio between the surface hardness at the temperature of 0° C. and    the surface hardness at the temperature of 100° C., an image display    device superior in stability and, particularly, in response to the    change of the temperature should be obtained.-   (v) By preparing the ingredients for the particles regulating the    tensile break strength, an image display device superior in    stability and, particularly, in response to the change of the    temperature should be obtained.-   (vi) By preparing the ingredients for the particles regulating the    Izod impact strength, an image display device superior in stability    and, particularly, in response to the change of the temperature    should be obtained.-   (vii) By preparing the ingredients for the particles regulating the    abrasion loss (Taber), an image display device superior in stability    and, particularly, in response to the change of the temperature    should be obtained.-   (viii) By preparing the ingredients for the particles regulating the    tensile elastic modulus, an image display device having capability    of displaying the images superior in stability and, particularly, in    repetition durability should be obtained.-   (ix) By preparing the ingredients for the particles regulating the    flexural elastic modulus, an image display device having capability    of displaying the images superior in stability and, particularly, in    repetition durability should be obtained.-   (x) By preparing the ingredients for the particles regulating the    tear strength, an image display device having capability of    displaying the images superior in stability and, particularly, in    repetition durability should be obtained.-   (xi) By preparing a group of combined particles comprising mother    particles whereon many child particles of at least one kind adhere,    an image display device having capability of displaying the images    superior in repetition durability at a low driving voltage, cheap,    and achieving the compatibility of improving stability and reducing    the driving voltage should be obtained.-   (xii) By preparing the ingredients for the particles obtained by    surface treating fine particles with a solution of charge control    agent, attachment of charging ability over the particles should be    sufficiently carried out and an ideal flight and movement should be    realized in an occasion of forming an electric field, and    accordingly, favorable images with sufficient contrast should be    stably obtained.-   (xiii) By preparing the ingredients for the particles obtained by    resin coating them by means of spraying a solution of dissolving    resin, an aggregation of the particles should be prevented and    favorable images with extended longevity against repeating display    and with superior stability should be easily obtained.-   (xiv) By preparing the ingredients for the particles at least one    resin layer is formed as an outer layer over a spherical central    component by coating a resin comprising a component whose index of    refraction is different from that of the central component, an image    display device having capability of displaying white clearly,    quickly responsive, and superior in repetition durability at a low    driving voltage should be obtained.-   (xv) By preparing the ingredients for the particles involving an    indefinite particles Around which at least one resin layer is formed    by coating a resin comprising a component whose index of refraction    is different from that of the indefinite particles An image display    device having capability of displaying white clearly, quickly    responsive, and superior in repetition durability at a low driving    voltage should be obtained.-   (xvi) By preparing the ingredients for the particles containing a    resin component prepared by polymerizing at least one kind of    monomer selected from acrylic monomer, methacrylic monomer and    styrenic monomer, an image display device easily determining    positive or negative and ensuring surface charge density, capable of    charge control by the selection of the monomer or blending ratio,    quickly responsive, and superior in repetition durability at a low    driving voltage should be obtained.-   (xvii) By preparing the ingredients for the particles contained in a    mixture obtained by blending at least two kinds of said particles    different in both color and charge characteristic, and by settling a    difference between each surface charge density within the range of 2    to 150 μC/m², an ideal flight and movement of particle under the    formation of the electric field should be realized and accordingly,    favorable images with sufficient contrast and without any unevenness    should be stably obtained.

The image display device employing the particles for displaying imagesin accordance with the present invention is applicable to the imagedisplay unit for mobile equipments such as notebook-sized personalcomputers, PDAs, portable telephones, and so on; to the electron paperssuch as electronic books, electronic newspapers, and so on; to thebulletin boards such as signboards, posters, blackboards, and so on; tothe rewritable papers substituted for papers consumed by copy machinesor printers; to the image display unit for electronic calculators orhome electric appliance products; and to the card image display unit forpoint cards, etc.

1. Particles for displaying images used in an image display device whichdisplays images by flying and moving at least one group of particlesenclosed between a pair of facing substrates of which at least one istransparent and across the substrates, an electric field being applied,wherein the ingredients for the particles satisfy at least onerequirement among the following: (1) Span of ingredient particlediameter distribution defined by the following equation is less than 5:Span=(d0.9−d0.1)/d0.5 wherein d0.1 represents an ingredient particlediameter (μm) of the ingredient particles whose ratio of ingredientparticles equal to or less than d0.1 is 10%, d0.5 represents aningredient particle diameter (μm) defining that 50% of the ingredientparticles are greater than d0.5, and another 50% of the ingredientparticles are smaller than d0.5, d0.9 represents an ingredient particlediameter of the ingredient particles whose ratio of ingredient particlesequal to or smaller than d0.9 is 90% each in the ingredient particlediameter distribution; (2) in the case where the surfaces of theingredient particles are charged by applying a voltage of 8 kV onto aCorona generator deployed at a distance of 1 mm from the surface of theingredient particles, a surface potential of the ingredient particle 0.3second after the discharge is greater than 300 V; (3) a ratio between asurface hardness at 0° C. and a surface hardness at 100° C. is 1.7 orsmaller; (4) tensile break strength is 20 MPa or greater; (5) Izodimpact strength (with a notch) is 100 J/m or greater; (6) abrasion loss(Taber) is 22 mg or less; (7) tensile elastic modulus is 24.5 MPa orgreater; (8) flexural elastic modulus is 44.1 MPa or greater; (9) tearstrength is 100 kg/cm or greater; and (10) ingredient particles involveindefinite particles around which at least one resin layer is formed bycoating a resin comprising a component whose index of refraction isdifferent from that of the indefinite particles, wherein thesolvent-indissoluble ratio of the ingredient particles in a solventdefined by the following equation is 50% or greater:Solvent-indissoluble ratio (%)=(B/A)×100 wherein A represents the weightof said ingredient particles before they are immersed into the solvent,and B represents the weight of said ingredient particles after immersingthem in a non-defective solvent for 24 hours at the temperature of 25°C.
 2. Particles for displaying images used in an image display devicewhich displays images by flying and moving at least one group ofparticles enclosed between a pair of facing substrates of which at leastone is transparent and across the substrates, an electric field beingapplied, wherein the ingredients for the particles satisfy at least onerequirement among the following: (1) Span of ingredient particlediameter distribution defined by the following equation is less than 5:Span=(d0.9−d0.1)/d0.5 wherein d0.1 represents an ingredient particlediameter (μm) of the ingredient particles whose ratio of ingredientparticles equal to or less than d0.1 is 10%, d0.5 represents aningredient particle diameter (μm) defining that 50% of the ingredientparticles are greater than d0.5, and another 50% of the ingredientparticles are smaller than d0.5, d0.9 represents an ingredient particlediameter of the ingredient particles whose ratio of ingredient particlesequal to or smaller than d0.9 is 90% each in the ingredient particlediameter distribution; (2) in the case where the surfaces of theingredient particles are charged by applying a voltage of 8 kV onto aCorona generator deployed at a distance of 1 mm from the surface of theingredient particles, a surface potential of the ingredient particle 0.3second after the discharge is greater than 300 V; (3) a ratio between asurface hardness at 0° C. and a surface hardness at 100° C. is 1.7 orsmaller; (4) tensile break strength is 20 MPa or greater; (5) Izodimpact strength (with a notch) is 100 J/m or greater; (6) abrasion loss(Taber) is 22 mg or less; (7) tensile elastic modulus is 24.5 MPa orgreater; (8) flexural elastic modulus is 44.1 MPa or greater; (9) tearstrength is 100 kg/cm or greater; and (10) ingredient particles involveindefinite particles around which at least one resin layer is formed bycoating a resin comprising a component whose index of refraction isdifferent from that of the indefinite particles, wherein a waterabsorption of the ingredient particles is 3% by mass or less. 3.Particles for displaying images used in an image display device whichdisplays images by flying and moving at least one group of particlesenclosed between a pair of facing substrates of which at least one istransparent and across the substrates, an electric field being applied,wherein the ingredients for the particles satisfy at least onerequirement among the following: (1) Span of ingredient particlediameter distribution defined by the following equation is less than 5:Span=(d0.9−d0.1)/d0.5 wherein d0.1 represents an ingredient particlediameter (μm) of the ingredient particles whose ratio of ingredientparticles equal to or less than d0.1 is 10%, d0.5 represents aningredient particle diameter (μm) defining that 50% of the ingredientparticles are greater than d0.5, and another 50% of the ingredientparticles are smaller than d0.5, d0.9 represents an ingredient particlediameter of the ingredient particles whose ratio of ingredient particlesequal to or smaller than d0.9 is 90% each in the ingredient particlediameter distribution; (2) in the case where the surfaces of theingredient particles are charged by applying a voltage of 8 kV onto aCorona generator deployed at a distance of 1 mm from the surface of theingredient particles, a surface potential of the ingredient particle 0.3second after the discharge is greater than 300 V; (3) a ratio between asurface hardness at 0° C. and a surface hardness at 100° C. is 1.7 orsmaller; (4) tensile break strength is 20 MPa or greater; (5) Izodimpact strength (with a notch) is 100 J/m or greater; (6) abrasion loss(Taber) is 22 mg or less; (7) tensile elastic modulus is 24.5 MPa orgreater; (8) flexural elastic modulus is 44.1 MPa or greater; (9) tearstrength is 100 kg/cm or greater; and (10) ingredient particles involveindefinite particles around which at least one resin layer is formed bycoating a resin comprising a component whose index of refraction isdifferent from that of the indefinite particles, wherein a surfacehardness of the ingredient particles measured at the temperature of 25°C. in accordance with JIS K7215 is at least 40 degrees.
 4. A group ofparticles containing a mixture obtained by blending at least two kindsof said particles, wherein said particles are particles for displayingimages used in an image display device which displays images by flyingand moving at least one group of particles enclosed between a pair offacing substrates of which at least one is transparent and across thesubstrates, an electric field being applied, wherein the ingredients forthe particles satisfy at least one requirement among the following: (1)Span of ingredient particle diameter distribution defined by thefollowing equation is less than 5:Span=(d0.9−d0.1)/d0.5 wherein d0.1 represents an ingredient particlediameter (μm) of the ingredient particles whose ratio of ingredientparticles equal to or less than d0.1 is 10%, d0.5 represents aningredient particle diameter (μm) defining that 50% of the ingredientparticles are greater than d0.5, and another 50% of the ingredientparticles are smaller than d0.5, d0.9 represents an ingredient particlediameter of the ingredient particles whose ratio of ingredient particlesequal to or smaller than d0.9 is 90% each in the ingredient particlediameter distribution; (2) in the case where the surfaces of theingredient particles are charged by applying a voltage of 8 kV onto aCorona generator deployed at a distance of 1 mm from the surface of theingredient particles, a surface potential of the ingredient particle 0.3second after the discharge is greater than 300 V; (3) a ratio between asurface hardness at 0° C. and a surface hardness at 100° C. is 1.7 orsmaller; (4) tensile break strength is 20 MPa or greater; (5) Izodimpact strength (with a notch) is 100 J/m or greater; (6) abrasion loss(Taber) is 22 mg or less; (7) tensile elastic modulus is 24.5 MPa orgreater; (8) flexural elastic modulus is 44.1 MPa or greater; (9) tearstrength is 100 kg/cm or greater; and (10) the ingredient particlesinvolve indefinite particles around which at least one resin layer isformed by coating a resin comprising a component whose index ofrefraction is different from that of the indefinite particles, whereinsaid ingredient particles are different in both color and chargecharacteristics, and wherein the group of ingredient particles have adifference between each surface potential in the case where the surfacesof the ingredient particles are charged by applying a voltage of 8 kVonto a Corona generator deployed at a distance of 1 mm from the surfaceof each ingredient particle is 100 V or smaller at 0.3 second after thedischarge.
 5. Particles for displaying images used in an image displaydevice which displays images by flying and moving at least one group ofparticles enclosed between a pair of facing substrates of which at leastone is transparent and across the substrates, an electric field beingapplied, wherein the ingredients for the particles satisfy at least onerequirement among the following: (1) Span of ingredient particlediameter distribution defined by the following equation is less than 5:Span=(d0.9−d0.1)/d0.5 wherein d0.1 represents an ingredient particlediameter (μm) of the ingredient particles whose ratio of ingredientparticles equal to or less than d0.1 is 10%, d0.5 represents aningredient particle diameter (μm) defining that 50% of the ingredientparticles are greater than d0.5, and another 50% of the ingredientparticles are smaller than d0.5, d0.9 represents an ingredient particlediameter of the ingredient particles whose ratio of ingredient particlesequal to or smaller than d0.9 is 90% each in the ingredient particlediameter distribution; (2) in the case where the surfaces of theingredient particles are charged by applying a voltage of 8 kV onto aCorona generator deployed at a distance of 1 mm from the surface of theingredient particles, a surface potential of the ingredient particle 0.3second after the discharge is greater than 300 V; (3) a ratio between asurface hardness at 0° C. and a surface hardness at 100° C. is 1.7 orsmaller; (4) tensile break strength is 20 MPa or greater; (5) Izodimpact strength (with a notch) is 100 J/m or greater; (6) abrasion loss(Taber) is 22 mg or less; (7) tensile elastic modulus is 24.5 MPa orgreater; (8) flexural elastic modulus is 44.1 MPa or greater; (9) tearstrength is 100 kg/cm or greater; and (10) ingredient particles involveindefinite particles around which at least one resin layer is formed bycoating a resin comprising a component whose index of refraction isdifferent from that of the indefinite particles; or the ingredientparticles at least whose surface are formed with a resin obtained byadding a charge control agent, wherein said charge control agent is atleast one kind of chemical compound selected from, resin acid modifiedazine, resin acid modified azine compound and phenolic condensate. 6.Particles for displaying images used in an image display device whichdisplays images by flying and moving at least one group of particlesenclosed between a pair of facing substrates of which at least one istransparent and across the substrates, an electric field being applied,wherein the ingredients for the particles satisfy at least onerequirement among the following: (1) Span of ingredient particlediameter distribution defined by the following equation is less than 5:Span=(d0.9−d0.1)/d0.5 wherein d0.1 represents an ingredient particlediameter (μm) of the ingredient particles whose ratio of ingredientparticles equal to or less than d0.1 is 10%, d0.5 represents aningredient particle diameter (μm) defining that 50% of the ingredientparticles are greater than d0.5, and another 50% of the ingredientparticles are smaller than d0.5, d0.9 represents an ingredient particlediameter of the ingredient particles whose ratio of ingredient particlesequal to or smaller than d0.9 is 90% each in the ingredient particlediameter distribution; (2) in the case where the surfaces of theingredient particles are charged by applying a voltage of 8 kV onto aCorona generator deployed at a distance of 1 mm from the surface of theingredient particles, a surface potential of the ingredient particle 0.3second after the discharge is greater than 300 V; (3) a ratio between asurface hardness at 0° C. and a surface hardness at 100° C. is 1.7 orsmaller; (4) tensile break strength is 20 MPa or greater; (5) Izodimpact strength (with a notch) is 100 J/m or greater; (6) abrasion loss(Taber) is 22 mg or less; (7) tensile elastic modulus is 24.5 MPa orgreater; (8) flexural elastic modulus is 44.1 MPa or greater; (9) tearstrength is 100 kg/cm or greater; and (10) ingredient particles involveindefinite particles around which at least one resin layer is formed bycoating a resin comprising a component whose index of refraction isdifferent from that of the indefinite particles, wherein said indefiniteparticles are coated with a resin and wherein the coating amount of saidresin is 0.01 to 30% by weight of the amount of said indefiniteparticles.
 7. Particles for displaying images used in an image displaydevice which displays images by flying and moving at least one group ofparticles enclosed between a pair of facing substrates of which at leastone is transparent and across the substrates, an electric field beingapplied, wherein the ingredients for the particles satisfy at least onerequirement among the following: (1) Span of ingredient particlediameter distribution defined by the following equation is less than 5:Span=(d0.9−d0.1)/d0.5 wherein d0.1 represents an ingredient particlediameter (μm) of the ingredient particles whose ratio of ingredientparticles equal to or less than d0.1 is 10%, d0.5 represents aningredient particle diameter (μm) defining that 50% of the ingredientparticles are greater than d0.5, and another 50% of the ingredientparticles are smaller than d0.5, d0.9 represents an ingredient particlediameter of the ingredient particles whose ratio of ingredient particlesequal to or smaller than d0.9 is 90% each in the ingredient particlediameter distribution; (2) in the case where the surfaces of theingredient particles are charged by applying a voltage of 8 kV onto aCorona generator deployed at a distance of 1 mm from the surface of theingredient particles, a surface potential of the ingredient particle 0.3second after the discharge is greater than 300 V; (3) a ratio between asurface hardness at 0° C. and a surface hardness at 100° C. is 1.7 orsmaller; (4) tensile break strength is 20 MPa or greater; (5) Izodimpact strength (with a notch) is 100 J/m or greater; (6) abrasion loss(Taber) is 22 mg or less; (7) tensile elastic modulus is 24.5 MPa orgreater; (8) flexural elastic modulus is 44.1 MPa or greater; (9) tearstrength is 100 kg/cm or greater; and (10) ingredient particles involveindefinite particles around which at least one resin layer is formed bycoating a resin comprising a component whose index of refraction isdifferent from that of the indefinite particles, wherein said ingredientparticles are coated with a resin and wherein, defining the averageingredient particle diameter d_(0.5) before coating resin as r_(a) anddefining the average ingredient particle diameter d_(0.5) after coatingresin as r_(b), a changing factor: R=r_(b)/r_(a) is 5 or smaller, andwherein d_(0.5) represents an ingredient particle diameter (μm) definingthat 50% of the ingredient particles are greater than d_(0.5), andanother 50% of the ingredient particles are smaller than d_(0.5). 8.Particles for displaying images used in an image display device whichdisplays images by flying and moving at least one group of particlesenclosed between a pair of facing substrates of which at least one istransparent and across the substrates, an electric field being applied,wherein the ingredients for the particles satisfy at least onerequirement among the following: (1) Span of ingredient particlediameter distribution defined by the following equation is less than 5:Span=(d0.9−d0.1)/d0.5 wherein d0.1 represents an ingredient particlediameter (μm) of the ingredient particles whose ratio of ingredientparticles equal to or less than d0.1 is 10%, d0.5 represents aningredient particle diameter (μm) defining that 50% of the ingredientparticles are greater than d0.5, and another 50% of the ingredientparticles are smaller than d0.5, d0.9 represents an ingredient particlediameter of the ingredient particles whose ratio of ingredient particlesequal to or smaller than d0.9 is 90% each in the ingredient particlediameter distribution; (2) in the case where the surfaces of theingredient particles are charged by applying a voltage of 8 kV onto aCorona generator deployed at a distance of 1 mm from the surface of theingredient particles, a surface potential of the ingredient particle 0.3second after the discharge is greater than 300 V; (3) a ratio between asurface hardness at 0° C. and a surface hardness at 100° C. is 1.7 orsmaller; (4) tensile break strength is 20 MPa or greater; (5) Izodimpact strength (with a notch) is 100 J/m or greater; (6) abrasion loss(Taber) is 22 mg or less; (7) tensile elastic modulus is 24.5 MPa orgreater; (8) flexural elastic modulus is 44.1 MPa or greater; (9) tearstrength is 100 kg/cm or greater; and (10) ingredient particles involveindefinite particles around which at least one resin layer is formed bycoating a resin comprising a component whose index of refraction isdifferent from that of the indefinite particles, wherein the ingredientsfor the particles are a group of combined ingredient particlescomprising mother particles whereon many child particles of at least onekind adhere; and the ratio (B/A) between the average particle diameterd_(0.5) (B) of the child particles and the average particle diameterd_(0.5) (A) of the mother particles is 20 or greater, and whereind_(0.5) represents a particle diameter (μm) defining that 50% of themother particles and child particles are greater than d_(0.5), andanother 50% of the mother particles and child particles are smaller thand_(0.5).
 9. Particles for displaying images used in an image displaydevice which displays images by flying and moving at least one group ofparticles enclosed between a pair of facing substrates of which at leastone is transparent and across the substrates, an electric field beingapplied, wherein the ingredients for the particles satisfy at least onerequirement among the following: (1) Span of ingredient particlediameter distribution defined by the following equation is less than 5:Span=(d0.9−d0.1)/d0.5 wherein d0.5 represents an ingredient particlediameter (μm) of the ingredient particles whose ratio of ingredientparticles equal to or less than d0.1 is 10%, d0.5 represents aningredient particle diameter (μm) defining that 50% of the ingredientparticles are greater than d0.5, and another 50% of the ingredientparticles are smaller than d0.5, d0.9 represents an ingredient particlediameter of the ingredient particles whose ratio of ingredient particlesequal to or smaller than d0.9 is 90% each in the ingredient particlediameter distribution; (2) in the case where the surfaces of theingredient particles are charged by applying a voltage of 8 kV onto aCorona generator deployed at a distance of 1 mm from the surface of theingredient particles, a surface potential of the ingredient particle 0.3second after the discharge is greater than 300 V; (3) a ratio between asurface hardness at 0° C. and a surface hardness at 100° C. is 1.7 orsmaller; (4) tensile break strength is 20 MPa or greater; (5) Izodimpact strength (with a notch) is 100 J/m or greater; (6) abrasion loss(Taber) is 22 mg or less; (7) tensile elastic modulus is 24.5 MPa orgreater; (8) flexural elastic modulus is 44.1 MPa or greater; (9) tearstrength is 100 kg/cm or greater; and (10) ingredient particles involveindefinite particles around which at least one resin layer is formed bycoating a resin comprising a component whose index of refraction isdifferent from that of the indefinite particles, wherein the ingredientsfor the particles are a group of combined ingredient particlescomprising mother particles whereon many child particles of at least onekind adhere; and the average particle diameter d_(0.5) of the childparticles is 1 μm or smaller, and wherein d_(0.5) represents a particlediameter (μm) defining that 50% of the child particles are greater thand_(0.5), and another 50% of the child particles are smaller thand_(0.5).
 10. Particles for displaying images used in an image displaydevice which displays images by flying and moving at least one group ofparticles enclosed between a pair of facing substrates of which at leastone is transparent and across the substrates, an electric field beingapplied, wherein the ingredients for the particles satisfy at least onerequirement among the following: (1) Span of ingredient particlediameter distribution defined by the following equation is less than 5:Span=(d0.9−d0.1)/d0.5 wherein d0.1 represents an ingredient particlediameter (μm) of the ingredient particles whose ratio of ingredientparticles equal to or less than d0.1 is 10%, d0.5 represents aningredient particle diameter (μm) defining that 50% of the ingredientparticles are greater than d0.5, and another 50% of the ingredientparticles are smaller than d0.5, d0.9 represents an ingredient particlediameter of the ingredient particles whose ratio of ingredient particlesequal to or smaller than d0.9 is 90% each in the ingredient particlediameter distribution; (2) in the case where the surfaces of theingredient particles are charged by applying a voltage of 8 kV onto aCorona generator deployed at a distance of 1 mm from the surface of theingredient particles, a surface potential of the ingredient particle 0.3second after the discharge is greater than 300 V; (3) a ratio between asurface hardness at 0° C. and a surface hardness at 100° C. is 1.7 orsmaller; (4) tensile break strength is 20 MPa or greater; (5) Izodimpact strength (with a notch) is 100 J/m or greater; (6) abrasion loss(Taber) is 22 mg or less; (7) tensile elastic modulus is 24.5 MPa orgreater; (8) flexural elastic modulus is 44.1 MPa or greater; (9) tearstrength is 100 kg/cm or greater; and (10) ingredient particles involveindefinite particles around which at least one resin layer is formed bycoating a resin comprising a component whose index of refraction isdifferent from that of the indefinite particles, wherein the ingredientsfor the particles are a group of combined ingredient particlescomprising mother particles whereon many child particles of at least onekind adhere; and Span of ingredient particle diameter distributiondefined by the following equation is less than 5:Span=(d _(0.9) −d _(0.1))/d _(0.5), and wherein d0.1 represents aningredient particle diameter (μm) of the ingredient particles whoseratio of ingredient particles equal to or less than d0.1 is 10%, d0.5represents an ingredient particle diameter (μm) defining that 50% of theingredient particles are greater than d0.5, and another 50% of theingredient particles are smaller than d0.5, d0.9 represents aningredient particle diameter of the ingredient particles whose ratio ofingredient particles equal to or smaller than d0.9 is 90% each in theingredient particle diameter distribution.
 11. Particles for displayingimages used in an image display device which displays images by flyingand moving at least one group of particles enclosed between a pair offacing substrates of which at least one is transparent and across thesubstrates, an electric field being applied, wherein the ingredients forthe particles satisfy at least one requirement among the following: (1)Span of ingredient particle diameter distribution defined by thefollowing equation is less than 5:Span=(d0.9−d0.1)/d0.5 wherein d0.5 represents an ingredient particlediameter (μm) of the ingredient particles whose ratio of ingredientparticles equal to or less than d0.1 is 10%, d0.5 represents aningredient particle diameter (μm) defining that 50% of the ingredientparticles are greater than d0.5, and another 50% of the ingredientparticles are smaller than d0.5, d0.9 represents an ingredient particlediameter of the ingredient particles whose ratio of ingredient particlesequal to or smaller than d0.9 is 90% each in the ingredient particlediameter distribution; (2) in the case where the surfaces of theingredient particles are charged by applying a voltage of 8 kV onto aCorona generator deployed at a distance of 1 mm from the surface of theingredient particles, a surface potential of the ingredient particle 0.3second after the discharge is greater than 300 V; (3) a ratio between asurface hardness at 0° C. and a surface hardness at 100° C. is 1.7 orsmaller; (4) tensile break strength is 20 MPa or greater; (5) Izodimpact strength (with a notch) is 100 J/m or greater; (6) abrasion loss(Taber) is 22 mg or less; (7) tensile elastic modulus is 24.5 MPa orgreater; (8) flexural elastic modulus is 44.1 MPa or greater; (9) tearstrength is 100 kg/cm or greater; and (10) ingredient particles involveindefinite particles around which at least one resin layer is formed bycoating a resin comprising a component whose index of refraction isdifferent from that of the indefinite particles, wherein said ingredientparticles involve indefinite particles around which at least one resinlayer is formed by coating a resin comprising a component whose index ofrefraction is different from that of the indefinite particles and whichare white.
 12. Particles for displaying images used in an image displaydevice which displays images by flying and moving at least one group ofparticles enclosed between a pair of facing substrates of which at leastone is transparent and across the substrates, an electric field beingapplied, wherein the ingredients for the particles satisfy at least onerequirement among the following: (1) Span of ingredient particlediameter distribution defined by the following equation is less than 5:Span=(d0.9 −d0.1 )/d0.5 wherein d0.1 represents an ingredient particlediameter (μm) of the ingredient particles whose ratio of ingredientparticles equal to or less than d0.1 is 10%, d0.5 represents aningredient particle diameter (μm) defining that 50% of the ingredientparticles are greater than d0.5, and another 50% of the ingredientparticles are smaller than d0.5, d0.9 represents an ingredient particlediameter of the ingredient particles whose ratio of ingredient particlesequal to or smaller than d0.9 is 90% each in the ingredient particlediameter distribution; (2) in the case where the surfaces of theingredient particles are charged by applying a voltage of 8 kV onto aCorona generator deployed at a distance of 1 mm from the surface of theingredient particles, a surface potential of the ingredient particle 0.3second after the discharge is greater than 300 V; (3) a ratio between asurface hardness at 0° C. and a surface hardness at 100° C. is 1.7 orsmaller; (4) tensile break strength is 20 MPa or greater; (5) Izodimpact strength (with a notch) is 100 J/m or greater; (6) abrasion loss(Taber) is 22 mg or less; (7) tensile elastic modulus is 24.5 MPa orgreater; (8) flexural elastic modulus is 44.1 MPa or greater; (9) tearstrength is 100 kg/cm or greater; and (10) ingredient particles involveindefinite particles around which at least one resin layer is formed bycoating a resin comprising a component whose index of refraction isdifferent from that of the indefinite particles, wherein the ingredientparticles are insulating particles with volume specific resistance of1×10¹⁰ Ω·cm or greater.
 13. An image display device which displaysimages by flying and moving at least one kind of particles enclosedbetween a pair of facing substrates of which at least one is transparentand across the substrates, an electric field being applied, wherein saidparticles are particles for displaying images used in an image displaydevice which displays images by flying and moving at least one group ofparticles enclosed between a pair of facing substrates of which at leastone is transparent and across the substrates, an electric field beingapplied, wherein the ingredients for the particles satisfy at least onerequirement among the following: (1) Span of ingredient particlediameter distribution defined by the following equation is less than 5:Span=(d0.9−d0.1)/d0.5 wherein d0.1 represents an ingredient particlediameter (μm) of the ingredient particles whose ratio of ingredientparticles equal to or less than d0.1 is 10%, d0.5 represents aningredient particle diameter (μm) defining that 50% of the ingredientparticles are greater than d0.5, and another 50% of the ingredientparticles are smaller than d0.5, d0.9 represents an ingredient particlediameter of the ingredient particles whose ratio of ingredient particlesequal to or smaller than d0.9 is 90% each in the ingredient particlediameter distribution; (2) in the case where the surfaces of theingredient particles are charged by applying a voltage of 8 kV onto aCorona generator deployed at a distance of 1 mm from the surface of theingredient particles, a surface potential of the ingredient particle 0.3second after the discharge is greater than 300 V; (3) a ratio between asurface hardness at 0° C. and a surface hardness at 100° C. is 1.7 orsmaller; (4) tensile break strength is 20 MPa or greater; (5) Izodimpact strength (with a notch) is 100 J/m or greater; (6) abrasion loss(Taber) is 22 mg or less; (7) tensile elastic modulus is 24.5 MPa orgreater; (8) flexural elastic modulus is 44.1 MPa or greater; (9) tearstrength is 100 kg/cm or greater; and (10) ingredient particles involveindefinite particles around which at least one resin layer is formed bycoating a resin comprising a component whose index of refraction isdifferent from that of the indefinite particles, wherein cavitiesbetween said substrates are saturated with air having relative humidityof 60% RH or smaller at 25° C.